We have the same kind and it is a pig, when it comes to feeding time. Like brainrush said, just lay some small food on it when it is looking all fuzzy which sometimes can take a few hours after lights out for ours. I usually give ours mysis or bloodworms but anything meaty and small will work fine. It can take awhile for it to eat them and it works best if you can shut off your powerheads so they don't blow the food off. As for the turning white though, I would check your calcium and alkalinity levels as well since these are LPS and need the calcium to be stable in the tank. Also, what kind of flow is hitting it? They like a moderate amount of flow but nothing too drastic. Also, I see that it is at the bottom of your tank. They tend to be light hogs as almost all LPS are, so moving it up may help as well. Posting all your water parameters would help a lot though, the actual values, not just good.