i was wondering if there could be anything esle besides hight temps that causes crispy leaves. the leaves i am talking about r also folding in half, like each finger is foldin at the main vein.
Are the leaves folding/rolling under? If so are the leaves themselves curved down, like if you held your hand out and turned your finger down? Are the leaves folding/rolling upward? Is there any discoloration, any bluish or purplish or reddish color showing anywhere on the leaves? Are the leaves very dark green but a dull green? Is there any necrosis, brown patches or spots? If so are they between the veins? Are the veins dark green? Where on the plant(s) did this begin, lower, middle, upper? Is it the large fan leaves, smaller leaves or all leaves? Have you noticed any change in the amount of water used, as in the plant(s) using less water than in the past, needing to be watered less frequently? How old are your plants? Have you been fertilizing them? If so with what and how often and in what amounts? Do you know what your pH is? Are you growing in soil, hydro or aero? How high are your temperatures?
Can you post a clear picture of a leaf or a few leaves that are affected and also one of an entire plant?
We need a lot more info to be able to answer your question with anything more than just saying, yes, there are things other than high temperatures that could cause what you are seeing.