Heat/light stress appears to be the problem. The plants' leaves are curling because it's trying to transpire as much as possible; this is called evaporative cooling.

Notice the lower leaves are not so much affected when compared to the higher leaves. 1000W is a lot of output! The lights being 6" from the canopy is far too close, even with a cool tube and fan blowing over the canopy; raise them 6"-12" and you should see improvement.
purpleskunk777 Reviewed by purpleskunk777 on . leaf curl due to heat maybe? Hey hows it going, Ive done a lot of research on this but I'm still unsure of the exact cause. L=soilless SunshineMix#4) D=no E= EVERYONE needs to answer lol! E-indoor E- soilless Rating: 5