Tank looks beautiful. Nicely done!
How did you come to realize your STN was related to too much light?
After doing some lighting research and realizing my lights were on (T5s + LED hybrid) for too long @ 12hours and too high of PAR @ 350+. I since reduced the T5s to just 6 hours a day, have the LEDs on a low ramp, and lowered their intensity so my PAR is in the 250-270 range during the peak 6 hour period, and <100 during the off hour ramp periods.
It could be other factors as well - but a lot of the SPS that had stunted growth and brown color immediately started to color up again once I made this change, and all of the Acropora I have added to the tank since seem to be hanging on now.