The first things that comes to my mind when I see tissue recession in lps is an unstable alkalinity level, next is too much lighting and last lack of supplemental feedings. It would seem like since the coral is over illuminated the coral would be not need supplemental feedings but these types of lps do much better and maintain coloration with supplemental feeding of a fine meaty sea food or quality pellets.
It's all a mote point though if chemistry is the issue. So check and track your chemistry, and adjust and maintain target values. An alk value between 8-10 is fine, but pick a number and strive to main that value. Ca 350-450, I like in the mid 400's, Again consistency is the key.
Are you doing water changes?