Probably heat damage, at 88F. Are you adding any ferts to the leaves or spilling fert on them? If you spill fert on leaves, it will kill the leaves in areas just like what you have there. If not, then it's heat damage.
polishpollack Reviewed by polishpollack on . 22 Days Flowering - What the HELL is going on with my fan leaves? %$&?* Highest Temp (lights on) 88Deg. F Lowest Temp (lights off) 74Deg. F Highest humidity 60% Lowest humidity 33% Fans always on when lights on Fans come on for 15 mins every hour when lights off Leaves affected are mainly lower to mid fan leaves. Areas of damage have a dry crispy feel as well as the green on the same leaf. Papery feel. Not all leaves feel this way, just the ones with areas of damage. Rating: 5