bottom leaves turning yellow and droping off please help

93 degrees is way too hot in my opinion and the fluctuation in temperature isn't helping either. I keep mine very consistent at around 75-85 degrees F. For being 43 days old, those plants are terribly stunted. What kind of soil are you using? Nutrients? Does your fan bring outside air into the tent? Anytime you grow in an enclosed space you need to make sure the plants get plenty of good quality rich air from outside (not from inside your house).

 

The single biggest factor on growth is the ph of the soil. Before trying other things i would make sure your 110% positive that your ph is correct. Certain ph meters aren't always accurate. Try using ph strips to test the water run off and a reliable meter and compare the results. I have had plants that had nutrient lock which in turn locks out nitrogen and other critical growth nutrients. I was never a big fan of coco. Coco tends to build up unwanted salts more than peat based mixes. Next time you plant, i would recommend using a peat moss based soil less mix or a good potting soil like fox farm. My recommendation is to give them a good flush (4 times the volume of you containers) with luke warm water to clean out some of the salts and then re-check the ph using test strips and a meter. Once you are sure the ph is correct, start feeding with a nitrogen rich fertilizer.

 

Keep in mind that heat rises. Make sure your intake is coming in through the bottom of the tent so the fresh air isnt just blowing out your exhaust. The air should circulate before getting removed from the tent. Put the intake and exhaust on opposite sides so it creates a spiral moving around the tent. I have had very good luck with this little trick.

 

I'm going to have to respectfully disagree with this entire post.

First of all, the single biggest factor on growth is the growing environment. Temperature is not more important than humidity, which is no more important than light, or fresh air. Each of these components must be present for success and to focus on pH balancing in coco would be to put far too much attention to an area which requires little to know attention from a gardener.

If you were having pH issues, given the age and size of the plants, you should see "pH spotting" on the leaves. This is not the case and you do not have any evidence of high or low pH in your media. Coco is EXTREMELY self-sufficient when it comes to buffering the pH level which is one of many reasons Coco is a far superior media to Sphagnum Peat.

pH strips are far too inaccurate for the job at hand. These strips depend on the color of the litmus paper to change and for a comparative analysis of the color against a chart which is unreliable in this setting; at best. A reliable pH meter is all a person needs and these can be purchased for $40 on the average (cheaper models will be less reliable and require more frequent calibration which will cost you money).

In addition, the pH of the runoff of coco is not the pH of the media itself. Coco will regularly run off higher then the solution used. It is usually somewhere in the 6.3pH to 6.7pH range. To get an accurate idea of the pH of the media you need to do a slurry test by collected a good amount of coco from as deep into the planter as you can and putting it in a cup. Then you add a little Deionized water to make a kind of slurry and place the pH tester right down in there.

For the last year I haven't cared in the slightest about my pH being "perfect" with coco. Stuff does a lot of the heavy lifting. All I worry about is getting close. Coco seems to manage organic acids very well also and this has lead me to replace my Phosphoric Acid pH down from General Hydroponics with a Fulvic Acid supplement called FlavorFul from Humboldt Nutrients. There are a number of benefits to using an Organic Acid like Fulvic as a pH down rather than H2PO4. Instead of using a Potassium Bicarbonate (or worse, a sodium bicarbonate) as my pH up I use Dyna-Gro Pro-Tekt Potassium Silicate. I find that when supplementing 2-3ml of Pro-Tekt with 3-4ml of FlavorFul my pH balances out very nicely and holds the value for much longer then traditional pH solutions. The silica and the fulvic actually help too!

"Nutrient Lock" is a pretty broad term and is dependent upon the Salinity, ions playing off each other, of the solution and the media much more then simply the pH. Coco can retain a great deal of Cations due to the structure of the fibers. Some cations, like Sodium, are bad news bears in coco and it can build up to extreme levels which will cause issues. It is therefore very important to select nutrients which do not feature much sodium. The Cation bank of coco should be filled with Calcium to establish the real benefit of Coco called the Cation Exchange Capacity. The media retains a "high pressure" of elements which have electrical charges. The plant has a lower pressure of these elements. Due to the high CEC of Coco elements flow from the high pressure media into the low pressure plant. This is known as osmosis and it is the passive fundamental process which allows roots to draw up nutrition. Of all the things to understand about coco it is the balance of the Cation Bank. If the cation bank is overfilled and the gardener continues to push high levels of Calcium then issues with other cations will appear as the plant does not have access to the right balance of elements. Potassium and Magnesium and Potassium issues are common in coco due to Calcium/Sodium and the CEC because all of these elements are considered to be Electrically Positively Charged (each element on its own needs an extra electron to fill the electron cloud and this is how Sodium bonds with Chlorine out of solution).

Precipitation in Coco is a major concern for growers because of the presence of a good deal of elements in the media. When the media is allowed to dry out salts that were once dissolved in water (aka "in solution") are allowed to precipitate out of solution and bond - becoming salts. These are not "unwanted" salts because you should only be adding things you want to the reservoir. The only way an "unwanted" salts makes it into your system is if you put it there. Precipitation due to the moisture available in the media is an issue for most any media as precipitations are a feature of the universe and are not unique to coco.

Fox Farms has not been providing quality soil for quite some time. Several years ago they did a good job but the company simply cannot keep up with the demand for their product and as a result the quality faded. If a grower would like to move into soil then I would suggest researching several "Super Soil" recipes; like those of Tom Hill, Vic, Subcool, or Humboldt Local. There are many good organic pre-mixes available too like those from Root's Organics which I would always suggest first.

Warm water is a bad idea to add to your root zone. Can't remember the logistics of it, but it's something about the root zone requiring the proper temperature for health and immune functions. I know that when my reservoir temperatures are up over 70 degrees that I will get "Eagle Claw" that 90% of newer growers misdiagnose as Nitrogen Toxicity. In addition to the poor advice to use warm water you also don't ever want to run plain water through coco like that unless you are trying to flush the plant. Coco will wash out elements readily and by dropping the CEC you will only cause further issues by creating a low-pressure media forcing elements to be drawn out of the plant and further exaggerating the deficiency issues. If you are certain there is buildup in the media then you always use a very low strength nutrient solution and simply rinse the media until it is clean and the EC of the runoff is within a 30% deviance of the solution you are using. IE 0.5ec in and 0.65ec out. Once the media contains the proper balance of elements you are providing then you can continue to feed it as normal.

Now that I have dispelled all of that horrendous advice I can finally get to the issue at hand...

1. The proper pH for the solution is between 5.5pH and 6.5pH. You should drop your pH level from 7.0 to get into this range. As I suggested earlier, FlavorFul for $12 per quart will last you a long ass time and is well worth the investment. Mix your solution as usual and add 2-4ml of this stuff before feeding.

2. Your temperatures are a huge issue. The perfect temperature for indoor growing is 75.6 degrees and you're nowhere near this number. If the air outside if over 75.6 degrees then there is no way you're going to be able to use that air to cool your growing space. Your growing space cannot be cooler then the temperature of your intake and as a result most growers use Air Conditioning in the summer time to manage heat. I picked up a 5,000BTU AC window unit from Home Depot for $80 last year. When it comes down to spending $80 so that my growing environment is setup to produce ounces and ounces of buds... $80 is chump change compared to the pounds I will pull during its lifetime. Look around on craigslist or keep your eyes peeled for things like 20% off any purchase at hardware stores. Probably a little late in the season to try and track one down but this is going to be a very late summer and fall this year due to the La Nina winter we just had. Plan for more hot days and get your temperatures down. If the air in your apartment is cooler then the air outside the apartment then it just makes good sense to pull from the inside and exhaust the heat back out.

If you cannot get your temperatures under 85 consistently then it really doesn't matter if your nutrient solution is dialed in. Those plants aren't going to be happy in the 90's and it is just going to get worse. If I were you I would be focusing 100% of my attention on the growing environment by getting an AC unit to provide cool air for the plants.

With regards to your nutrient system you shouldn't be using Top Max during Veg. Also, BioBizz organic nutrients are not exceptionally high in the amount of Calcium the contain, so I would strongly encourage you to purchase either Botanicare's Cal-Mag+ or General Organics CaMg+. Just 2-3ml from either could be a difference maker.

Keep your runoff volumes up over 30%, don't let the media dry out anymore, watch your runoff EC to make sure it is not much higher then the solution you are using, and keep the temperatures in line and you'll find those plants will explode on you in flowering.

Good luck. Let me know if you need anything.

 

1. It's coco, not soil.

2. If you read my previous post you'd see that coco MFG's, and myself, suggest that you NEVER FLUSH. Always Rinse.

3. Green is an indication of Algae growing in the media, likely as a result of your organic nutrients containing some Algae in combination with your unacceptably high temperatures. Bringing the temperatures down would slow/impede the growth of Algae in any system, including coco.

 

I dont think fox farm soil is all that bad. Yes, roots organics is higher quality and you probably cant beat a homemade "super soil" but fox farm still make a solid product in my opinion.