hanging light height?

[newfish]

I have a 55 gallon tank just LPS and few fish I have a odyssea duel 250w MH 14k with 4 t5's blues....I noticed my acans need to be under rocks (shaded from lights).or they loose there color they are placed on sandbed. My lights were 14 inches off the water. I have a fan running in between the tank and lights for heat of lights. I raised the lights to 18 inches is this ok to move them out from the shaded areas and not loose color? I don't want to stress them