Black sun coral question

[Kellyscoral]

Hello - I have a couple of orange sun corals as well as one black one. Had them all for about 8 or 9 months and they eat well and extend beautifully. About 6 weeks ago the black one started getting some white patches, it's still gets beautiful huge green polyps and eats well. Most of what I've researched suggest that this tends to happen to the black ones and that eventually it will die. Any thoughts or suggestions on this? I love these corals and would hate to have this guy die. Water parameters are all good and all my suns are in good flow areas down at the bottom of my tank. Thanks!