Heat Stress!

Plants are 6 weeks, in Bubbleponics, given premeasured nutes (Stealth), PPM 900-1100. I've had them under florescent light until this week. Still 18/6, I now have them in a large walk-in closet, ventilated, fan blowing, 650 W HPS. Temps were over 100 outside, so have used A/C, but grow room temp has hovered around 90º anyway. Humidity has hung around 40-50% all week in grow room (I live in the desert).
They were doing so well, but growing a little slow, so on the advice of someone here, I fired up the HID.
Three days after turning on the HPS, they started looking like this.
I know it's heat stress. I had the light 20" from top of plants. I've moved it to 30" from them; will they recover?
Is there anything else Io can do?
Should I go back to florescent until time to flower?

Have a fan blowing air around the room.out side the room you are growing in.you have a exaust fan right.unless you get a good exaust fan there is not much i can realy say.if it was me personaly i hate saying it but yes i think i would go back to the flouresents till flowering.but dude if you are liveing in the desert get the plants outdoors and bring them in at night,there has got to be somewhere you can put the plants to veg.man i would have plantations all over the place look for any green areas this means water is near by great place to bang a few plants in.