From the pictures it does just look like mild heat stress to me. Was the weather unusual while you were away from them? Sorry not more helpful.
sideshowmel Reviewed by sideshowmel on . First grow plants wilting need help asap 400 wtt metal halide two led red and blue panels...18 hours on came home to find all new growth wilting temp was around 75 to 80 but is a constant temp through this gwo period...... Very confused Rating: 5