SPS newly question

[Treebeard]

...newby, that's newby question! Thanks auto spell correct.
I have 90 gallon tank, coming up to its 4 birthday and recently replaced my T5s with a new 48" Sunbrite led fixture and decided to try some SPS. I have an acro and monti sitting about 10" from the surface and the lights are 5" from the water. Should I be running the lights at 100% for a few hours each day or is that too much? I have had the colonies for about 2 weeks but the acro seems to be bleaching out a little at the tips. The parameters are all good except the nitrates were running between 15-20 ppm depending which test kit you believed.