Could my nemo be sick?

[marcingo]

Hey everyone. Ive got a 55 gal tank with all soft corals. Just before Christmas I added a tube anenome. My inhabitants are two black false perculas a foxface and 2 false perculas and a goby. There is also a cleaner shrimp and peppermint shrimp. 2 weeks ago one of my false perculas dissapeared and I never found a body. This made me think that maybe the tube anenome ate it. The anenome is small and the percula was medium sized which made me think its rather unlikely. Anyway now I noticed one of my black perculas the smaller one seems to be hiding a lot. The colors on its body are dulling out. The other one is very black the white stripes are very bright and its yellow nose and fins are nice and bright. While the sick one has almost lost all the yellow on its nose and fins and this yellow has turned almost grey. It swims and acts pretty normal except for the fact that it hides in the rocks a lot. If anyone has any ideas what this could be and if it could be sick please let me know. My nitrates ammonia and nitrites are 0. Thanks.