Again, how long have you had it? Have you ever seen the poylops out like in the pic's I posted?
You may want to think about breaking off the section where it's turned grey and has the coraline on it before it spreads too much farther. As far as flow and light, I've kept mine over the years under just about all conditions and he's done fine. Started with 100W of PC and now have 175 W MH and 220 W PC and he's fine. They seem to be hardy corals. What are your water parameters?