What other corals are in the tank? If there are a lot of zoanthids, leathers and morphs, you could have a toxin build up. Nils seems to have your lighting sorted, maybe a few extra water changes will sort things out. When my tanks are looking like crap, I do a few 20% changes and that will rid the tanks of any built up toxins. If you're using NSW, there could be an issue there too.