Hammer coral looking bad

[Fastidious]

So out of nowhere my hammer coral decided to not open and started turning a bit brown and some are losing all pigment. My water is fine, tested and everything looked good. All other corals are fine as well. Just wondering if the little guy is dying and what I can do for it. It has been in my tank for a little over a week and haven't moved it since.

http://www.reefcentral.com/forums/attachment.php?attachmentid=209773&stc=1&d=1352146873

Thanks