I don't know much about this kind of stuff, but since I have an AI Sol light, I tend to catch threads about them on various forums. This seems rather common actually. Happened to me when I switched. AIs are major par outputters (that's not a word, I don't think). Even starting at a low setting it was probably pretty bright. Bumping up every week can be too fast from what I hear. I don't know how much you bumped up every week of course. This is kind of a shot in the dark, but once you've ruled everything else out, try turning your light way down and see how things react through the weeks. Like *way* down, even to where you started out. When I moved my light to over my nano, I was shocked at how low I'm running the light and all of my corals are thriving. LEDs can sure fool the eye!
Anyway, good luck figuring out what the problem could be. It's very frustrating to watch your corals recede.