not necessarily dehydrated, although that can be a problem, but the internal chemical reactions in the plant are outta whack and increased heat basically speeds up the rate at which they react wrong.. if that makes sense? Plants weakened by fertilizer imbalance are super duper sensitive to heat and light burns. In the thread 'foxysox is back in the game', i believe there is a very good pic from around MAy or June in which she shows a plant badly damaged by use of a bloom booster in high temps conditions.