I'm new too so probably not a lot of help. However, what I think of with white and cloudy is either spawning, shedding, or chemical warfare. I've never seen my Xenia do any of these though so I don't even know if they do that. The one I would be most worried about is the chemical part. Softies are know to release chemicals to keep other corals away. Are you running any Carbon? If not I would add some. In your picture it almost looks like there is something brown right next to it, is that another coral? The Xenia may be irritated by that and trying to get it to move away.