leaves curling under and edges looks like leaves wilting

I have 13 plants. Had spider mite problem. I used SMC-90 and did the 3 sprayings 3 days apart but then after a few days the curling started.Dont know if its heat stress or ph problem. I have 4 fans and one of them blows across canopy.White hairs are still reproducing.Looking for some help im a first time grower.THX