Hey guys and gals. I'm currently working on my 3rd grow, 1st in coco and I have 1 girl yellowing and other not. Both germed and sprouted same date. That isn't the issue. Issue is the 1 that's yellowing. Growing in ff cultivation nation 70 -30 coco perlite mix with hydroton on the bottom of the spring pots in autopots. And a couple hand fulls of hydroton mixed in. Using gh flora series nutrients, micro, grow, bloom, calimagic hydroguard, h202, nectar and cool bloom. Was using tap water until I noticed the yellowing and purchased a small r.o. filter. Tap water tested at .9 ec. Is now 0.0..f.n yay....anyway using the nutes at 1/2 strength. Reduced grow to 1/4 and increased bloom to 3/4 When flower started.. any recommendations would be appreciated..@olderfart, and
@St. Tom.. checked ph in the trays and found 6.7. Drained it twice and refilled with 5.5... I may have to flush,, ah.. been keeping the res at 5.6.. but it seems to sit too long in the tray.. ph rises..
First of all, your problem plant is not too bad yet, I have taken decent harvest from plants that looked a lot worse at this stage.
The problem looks like either nute buildup or ph, I can't tell which from the photo. PH of 6.7 in your tray suggests that pH is at least part if not the entire issue, but I'm too new at this mischief to be sure. In any case, I think that since you are in coco, I would flush that plant well with the pH ~5.8 bloom nute mix that you want to continue with, and keep flushing until the runoff is pretty much the same as the input. This should get the medium back where you want it. This will take a lot of nute mix. I have used entire laundry tubs of it to flush a few 3 gallon pots. You could consider a pre-emptive flush of the second plant as it is likely headed in the same direction, but slower.
The question is what next, and I have to say that if you are going to be around for the rest of the grow, I would just ditch the autopot fertigation, and go with top watering to 10-20% runoff. I have given up on autopots for salt nutes with cannabis. Others here make it work, most of the time, but I have had nute issues with every single salt grow on this system - I have always had a decent harvest, but invariably from plants less healthy than I would like. Autopots work well with soil, but IMO, are not the best solution with salt nutes whatever the medium. Just my 2 cents mind you, others will differ.
If you stick with autopot irrigation, I would flush both plants weekly to try to prevent the medium from getting out of whack again, and you need to keep the EC lower than you would with top irrigation - no higher than ~900EC in my estimation, maybe lower. If you see tips of fans starting to lighten in color, EC is too high. Your problem plant has, given the leaf tips, seen EC out of bounds already, but that could be from buildup in the medium, so it does not inform whether your mix so far is too high.
I should point out that I am not specifically familiar with the nute mix that you are using, so I do not know if there is something potentially wrong there. Sometimes the extra's have more to do with marketing than need, and I suspect that on occasion they can throw the nute balance out enough to cause issues.
I'll wrap this up by mentioning that if you want to use coco, Cocoforcannabis.com is worth studying at some length. The owners of the site know what they are doing and have documented their experience well. The site has an excellent description of DIY automated top watering system which I am now using after testing it in my last solo grow.
Sorry for the late reply, I was not ignoring you, your alerts just got buried among others somehow.
