My pink favia got a light spot after I had it for maybe a month. It was high in the rock work under VHO. I moved it slightly lower in the tank.
I've since switched to T5. He still has the light patch. It's been several months.
If it keeps getting lighter, I'd recommend moving it to the bottom of the tank. With those bulbs, you MIGHT be getting too high light if you didn't acclimate him.
On the other hand, he may be just fine and not get any worse.