zoa placement in tank

[JenniferL]

My tank is a 55g corner bow front. I have 4 x24W T5HO lights 2 actinic and 2 plain white. Only be 24" long due to the shape of the tank. Water depth is about 21" deep. Lights are about 4" above glass cover. Anyway my question is how far away should zoa's be away from light. I bought 3 frags on the weekend, I have the neon pink ones on the top of my rock (about 14" away from light) along with the other frag and they are opening up but the other one is neon green with some others on there as well, but the neon is not opening at all yet but the others on the same rock are.
Also, a little off topic I have just started using RO water (did one change this morning) my phosphate reading in my tank is .5 ppm, and nitrates read 0 on one test kit and about 15-20 ppm on the other. is this too high for reef? Could this be causing them to stay closed?
Thanks