Hey Ace the exact same thing happened to my Giant wellso when I had it. It happened right after I went from SE to DE metal halides. It totally lost all its color but still puffed up and took food with its tentacles. I moved it from the middle of my tank to a darker corner on the bottom and after a few months it started getting its color back. I think th shock of coming from a lower lit place to bright sunlight causes them to expel their color, but as long as they keep eating they start to produce more.
Is Reef Madness Catchy???