I have five photos below. Two of my plants both sativas, 1 sour d. x choc. thai & 1 cough, are experiencing some leaf margin curl upwards and a pale border on some leaves and growing in numbers. My PH has been a little high (7.1-7.4) so I'm wondering if there is something locked out and if so what it might be. I Was able to lower my ph down to 6.5 and that's about where it's now. After consulting Cervante's Bible and a few other books, It looks closest to me to be a Sulfur Def.??? I am also wondering if this looks more like a nute burn. I am using FF Grow Big 6-4-4. They were already on the mend from A tent that had white PVC for the frame. Come to find out that white pvc at about 75 degrees F. Releases fumes that are phytotoxic. Just something to keep in mind. Anyway I gave them just under the "Heavy Feeding" on the bottle about 2tsp p/gallon, four days ago. Some of the leaf tips are sloping up, and some sloping down. Any advice is good advice. Thanks everyone.
i'd say it's the beginning of either a build-up or a lock-out... in both cases if you back up a little on the feeding doses and use ph-corrected water you should be fine.... ...but since it looks kinda unique it could also just be the symptoms of the pvc-poisoning, in which case it should take care of itself in a week or two... good luck kere
the first and last leaf looks like a magniesum lock out, thats probably due to the high pH. but its not bad correct the pH and if it doesnt go away its something else, the curling up and folding of the leaves is a sign of mg deficiency... but its also looks a little like heat stress (just cuse the room is at 75 doesnt mean the leaf surface is the same) but treat it like lack og mg, if they still fold then rais the lights
Are these fan leafs at the top of your plant ? If so it could be heat stress. Also is there any chance you got strong nutrient solution on the leaves, it could cause the burning.