I've been having the same problem pop up on two different grows (Afghan Kush and OG). It presents as one or sometimes both of the fan leaves at a node, usually on the lower half of the plant, turning a beige color at the tip and progresses towards the leaf stem. The progression happens in a pretty uniform manner - it reminds me of an arrow head - until the leaf eventually dies. I've posted about this before and was unable to get a uniform consensus. Some thought I was over-feeding, others under-feeding. I tried adjusting my nutrient solution in both directions to no avail. Any help would be appreciated.
Here are some specifics: WaterFarm/DWC. Using GH Flora Trio, CalMag, Fulvic Acid (Grandma Enggy's/AN). PPM ~400. RO water pH 5.5-6.1 400w MH Day Temps: 75-80. Night: 69-71 Let me know if any other info would be helpful.
Looks like a magnesium def. to me.... 400 PPM is pretty low as well for plants that size. I would doubt it's a burn, being that your ppms are low..... Try an Epsom salt flush at the rate of 1 table spoon per gallon for two days in a row, then flush the system and start over with fresh nutes. RO water NEEDS more cal-mag than tap water. Build your nutrient profile from 0 PPM's, add cal-mag and Epsom salt till you get 250 PPM, then add your micro and grow/bloom.... Good luck!
I personally would suggest a heavy flushing and discontinue Grandma Enggy's.. You see a lot of people do not understand that fulvic acids are organic acids that arise naturally in decomposing organic material called humus (humic acids). As with humic acids, fulvic acids also chelate inorganic nutrients and heavy metals such as calcium, magnesium, iron, cobalt, lead and potassium. Once the calcium and iron ions have been chelated they cannot react with phosphate, sulfur or oxygen and precipitate out of solution. And thus fulvic acid greatly increases the absorption through the cell membrane, across the cytoplasm and directly to the nucleus of cells themselves. So even though you're ppm is rather low (which I would like to confirm an accurate calibration), but even though your TDS is low, using the fulvic acid greatly increased the absorption rates, and you have nutrient burn..... Discontinue Grandma Enggy's, and I personally would discontinue Cal/Mag until I see sings of an issue... Also you want to buffer your water and you can do this my using 20% tap water or drop the RO's pH to 4.0, then wait a little bit, then take it back to a 7.0... Then mix your 3 part base and adjust the pH to 5.6 in veg..... But again, assuming you calibrate your meters on a monthly bases....
To be fair, they were showing the early signs of a calcium deficiency after I pulled them from my cloner. That damage is visible I the pics if you look really, really hard. My TDS meter is due for a calibration (it's been a month this past weekend), but the level is in line with what I expected them to be (50% strength of GH's basic week 1 schedule). Ph meter is calibrated weekly. Thanks for stopping by, Jake. I'll follow your advice and drop the calmag until needed and eliminate the fulvic acid entirely. I do have a couple of follow-up questions: 1) My tap water is on a well with a water softener. Should I be concerned about extra salts if I cut my RO water with it? 2) How do you define flush? Should I simply change the res or should I run plain water through the system for a set period of time? Thanks!
Anytime..... Ya you do not want to use the softener... So buffer the RO by the pH.... Take it down to a 4.0, let it set for 15 minutes or so to stabilize, then take it back to a 7.0, again let it set for a bit, confirm it still held the 7.0, then mix the nutrients in, and after you got the PPM where you want it, then adjust the pH where you want it, and again I run a 5.6 to 5.8 in veg.... I run a 5.8 to a 6.0 in flowering.... If I'm starting to see signs of a Mag issue in VEG, I first will up the pH to a 5.9 and see if that resolves the issue... Then of course if it does not, I'll hit the soup with Cal/Mag, and I like the CaliMag by GH... The flush, always try to flush from the top down and usually try to get at least 3 times the size of the bucket through it... So if I'm having an issue and I'm in 5gal buckets, then I want to run about 15gal through it.. Other than that, the in between quick flushes between res changes, a fast 5gal flush is fine for preventive maintenance... That way you're flushing the salts down and out, as opposed to flood and drain, which of course does not do as good of a job.. Sometimes you just cant do a top down flush, so then I would do a flood and drain several times.... If I'm fighting an issue and have to flood for a flush, I'll change the res out after 2-3 floods, then do 2-3 more..... Make sense???
[quote name='"jakesterjammin"'] Make sense??? [/quote] Makes perfect sense. Thanks. I was never sure if the method for flushing soil also applied to hydro mediums. I'm curious if you have any thoughts about GH's feed schedule. I know you've used their products in the past with great success. I've always thought their schedule seemed rather high (1000ppm by week 2 or 3). Would you follow their schedule the whole way through, or would you use say 50% of their recommendation? I have another batch of plants that started flowering (my first crop) and that was a long hard slog keeping them healthy. I still don't feel like I've truly locked down my soup. Any tips on their products would help immensely.
I'm sure the 3 times flush rule of thumb is an overkill, but IMPO, it's better to overkill then under kill in this case... Fuck I'd run 50gal through a bucket if I thought it would save my yield from a nute burn.... Well I use GH but not totally what they suggest... First off I only use the 3 part base, Floranector, and Koolbloom, and then Calimagic if needed (which is rare)... I watch my plants for the to tell me what's to hot and what's not.... Meaning, like say I'm in week 2 and at a 1000ppm, but after a couple days I see that the leaves are starting to get a wave to them, which does not look normal, well at that point I know 1000ppm is to hot for the strain in question, so I'll dump some nutes off, add fresh water back until I get to maybe 800ppm, and then watch the next couple days..... I do this NO MATTER what nutrient I'm using.... AN says run a 1050ppm, the past 3 days I'm at a 1450ppm, and they are responding VERY well to it.... And you can see my growth rates from the high TDS here....... Here is just 1 cola I got off the last round with GH's 3 part base, Floranector, and Koolbloom.....