Hi All, I have tried for a while and seem to get this problem with various mediums and without cal/mag suppliments. I have started canna nutes / coco with great initial results. Around the 2.5wk mark(ish) I start to get curl and light green rim on leaves. I have used standard guideline for canna nutes 7.4 then to 9.6ml/gal A/B (per website) and cal/mag at 5ml per gal, which I am sure is too much in hindsight. I aim for 6.0ph and have only used a single gal of nutes total since day 7-10. I believe this is a magnesium lockout due to my overuse of cal/mag. Am i too far gone or is there a way to reverse/salvage. I am flushing with plain water, two days in and no improvement. It seems to be getting worse. Thx in advance.
Others will come on here with more experience, but I will give you my opinion. First of all, I have found that it is generally not a good idea to flush the medium before harvest. This breaks down the buffers the nutrients delivered to the media which can cause further issues. The better way is to deliver the proper ratio nutrients and Get about 20 to 30% runoff every feed. Go to growguide.info and based upon your water EC and your volume you can determine the proper feeding schedule. I would leave off the calcium and magnesium supplementation until things settle out. I found that there is an increased need of these two nutrients but only in small amounts. Of course, make sure to pH the solution between 5.7 and 6.
first pic looks like she needs a little more N, but already being at 9.6ml/gallon of your base, it should be more than enough. in veg i maxed out at 8ml/gallon A&B of course, thats always strain dependent. some need more, some need less. ya just gotta find that sweet spot the 2nd and 3rd pics dont look bad at all. that little bit of light green color on the edges of the leaves, i personally wouldnt worry about it. dont sweat the small stuff like that 5ml of ca/mg may be a little much when i ran Canna in RO water, i would always bring my starting ppm's up to 200 with calmag. i only used about 2-3ml/gallon
I'm not sure about recovering them, that would be for others to answer. One thing I've done since going to 100% coco, is to use tap water instead of RO/Purified. I've never had anything that looks like a mineral problem since. My tap water is pretty hard too, about 550 ec out of the tap. Once I add a half teaspoon per gallon of Jack's fertilizer I'm up to like 750. Doesn't seem to hurt a darn thing. I just use white vinegar to ph to exactly 5.8 and water every day never letting it dry out ... I treat it like hydroponics. I water until about a half cup or more drains out each time. I'm set up in a shower stall, it just drains away. It's so easy, it doesn't even seem fair. I'm using Jack's classic fertilizer, tap water, and vinegar. That's it, it's medieval. I'm like a casual noobie, but my stuff looks like I'm a seasoned veteran. If I had to wager a paycheck on it, I'd suggest that you stop flushing because that one looks like he's starving already. Try mixing up a batch of nutes using tapwater that sat out for a day to get the chlorine out, and use that. No cal/mag, just nute.
If its the same plant in all the photos the yellowed first photo is likely the result of the white balance. I'm with tothehead saying this isn't something to do anything drastic about. This is not a natural magnesium deficiency, there are other causes. Also, it appears to be more related to potassium than anything else to me, so adding something like Epsom Salt might only exaggerate the problem. My suggestion is to make a solution of RO water, 2ml Cal-Mag Plus, and 5ml of A+B. This should provide an EC of around 0.8 to 1.0. Then pH down the solution to 5.5. Coco has an incredible ability to buffer the pH and erring on the low side and letting the coco bring the pH up is more effective than trying to get the coco to bring the pH down from a solution that is too alkaline. While I am on the subject, if you are using a phosphoric acid based pH down, like Gen Hydro's, stop using it. You'll have much better results using a nitric acid pH down like TechnaFlora's or an organic acid like citric crystals or Fulvic acid. Fulvic has the added benefit of breaking down precipitates and is my preferred pH down for coco. Humboldt Nutrients flavorful runs about $12 per quart and you only need an ml or two for a big change. Stick to your guns and just take it a little slower until she tells you she's hungry. Maintain you environment also, low humidity and high heat can stress the plant out and cause this sort of issue. 80f max, and keep your humidity over 50%.
I got the same problems .... but much much worse. I thought it was a deficiency ... so I added lime/cal/mag pebbles .... now I think it may be getting worse. Looks a bit like nute burn .... but the tops are yellow and getting a reddish brown around the edges. I d/l and read the books from ILGM.... not enough depth in either of those to grow anything. I'm looking for a book that is gonna cover everything .... help with decisions (e.g., I never knew you could use coco in a "non"- hydroponic application). Be grateful if someone could point me to some data so I could get better at this