From my look I think some of it has to do with the cocofiber.Not a fan of it as it doesnt hold the nutes well and overall I have found doesnt work to well.
i think you have something there, and maybe if i treated my nute diet more like a hydro set up instead of soil, they wouldn't be deficient now. come to think of it, now it makes sense why i was able to feed them full strength amounts (by the bottle specs) with every watering, because the strength of fox farm grow big and big bloom and recommended doses are probably based on soil, figuring it would have some nutes in it.
i do like the texture of the cocofiber, though, because it is still nice and loamy, and drains very well, but retains just the right amount of moisture. i'm sure the roots like the feel of the coco...
Second question I would have is you said using co2 boost and said would be venting soon...You do clear the co2 air out a couple times a day and bring in fresh o2 from outside between co2 reinjections correct as you have to still exchange the air occasionally or the plant can get this look.
on my next grow i'm gonna be venting the light to better control heat, especially with adding a good bit more light, but i hadn't thought about venting from the outside... trying to make things more sophisticated one little step at a time. i do go in the room once or twice a day, so when i open the door, it must exchange a little bit...
Also at 2-4 weeks flower I would have kept flowering with nutes then gave a 3-5 day flush with the coco as its not gonna hold to many nutes to long and can be flushed quickly.Yellowing dropping fans does happen at flowering end but seems a little excessive in the pictures.
i'm gonna put them back on nutes with the next watering, probably tomorrow, or the next day... i don't know if it'll help any of the yellow leaves become more green or not... hopefully a little, but i'm guessing they're gonna be toast (nothing is crispy, though, the yellow leaves are still supple)
You ph testing the water and run off water from the pot?
that is one thing i have not been doing anything with, other than testing the tap water every couple of weeks to make sure the city isn't dumping any extra chlorine in there out of the blue. tried letting the water sit early in the grow, but as it evaporates, the ph goes crazy, and the ph is fine right out of the tap, so i've been just giving water straight from there... besides, it gets nice and aerated with the spray hose from the kitchen sink. i will try to check the ph of the runoff and see what happens there with my next watering.
thanks for helpin fletch!