I would put it back to what it is used too if there is any green left and hope for the best.google:hps distance chart.work your plant gently in range next time.
also holding your hand above your plant tops will helps as you can feel if its to hot or just right so your plant gets enough light but without to much heat.
Depending on how bad the burn is you should be ok.
I have had this happen on several occasions. I continued with the same light cycle and raised the reflectors a bit. Water before they go dark and they should recover. I left most of the burnt leaves on for a few days until new growth formed above them and then clipped the worse ones.