I have a couple of 5in or more sexfaciatus gold. I've had them for about a year or so. They're probably about 1.5 yrs old. One of them, the more dominant one, has been pale (color fading) for about 2 or 3 weeks now. Definitely looks sick. Stays in his cave now most of the time and only comes out to feed sometimes. It used to be a bit more active and chases other fish out of it's cave. What's wrong? Anyone seen this? What to do?