.... well, AN nutes can self buffer the solution they are in, but not the entire pot,... the roots, soil herd both contribute to pH in there, and the nutes aren't made to deal with that! I see no sign of nute burn issues,...
...How low is the RH? Temps are not bad by themselves, but as pop22 mentioned, any combination of higher temps, low RH, breeze strength/directness, even light proximity can trigger heat/light/transpiration stress,...and strain to strain tolerances certainly can vary.... 2 possibilities here, maybe some of both: the above mentioned env. and strain issues, and there's is some reference to atypical Mg defc. symptoms that involve edge curling,... I see some interveinal funkiness that could pass for it,.. I also now see some lowers with K-related symptoms (burning right at the "teeth" tips)... again, the coco could be part of this, because early symptoms of K defc. and toxicity can cause this type of teeth tip burning!
recall, coco has native K in it,... and it's a Ca hog,.. might be that there's still not enough Ca-Mg going in to satsify the coco, which will bind it up and keep it from the plant,... And of course, pH is still an unknown here, so is in play as part of the problem.. If you don't have a good soil pH probe, you have to use the run-off method, which I dislike for all it's inherent inaccuracies, but there is an im proved methodology here-->
https://www.autoflower.org/threads/...-for-run-off-testing-and-ph-estimation.41733/
...run this test and calculation and mind the directions to the letter,... it will involve watering them heavily, which is fine, since it's likely a flush will be needed to try and reset the coco CEC and pH with a Ca-Mg heavy, light nute solution,.. betting if anything, it's too acidic in there,... seems too early for salt build-up too, BTW,....
