Hi, I bought this guy the two days ago. I noticed this spot yesterday and was very faint. Today it has gotten darker and maybe pushing out against it's skin. I don't remember seeing this when I purchased it. He is picking at the rock, has eaten some seaweed and some frozen brine shrimp. He is showing the normal color changes; white spots, dark color and then changing back to it's normal colors. I have read that it could be a number of things but most of them have spread, this is the only spot so far. He is housed with two clowns, two firefish, a pajama cardinal and royal grammar. Thanks in advance.