help w/pic

Alright and yeah the fans all turn on and shut off 1/2 hour before the light. The other 3 plants art showing anyproblems as of yet. I just flushed both plants with plain pHed water see if there is a change till next watering

I also thought it was heat stress at first but it started at the bottom of the plant and has move it's way up effecting more and more leafs.