ok I've had my sun cat for about 2 weeks now and when I bought him he was kinda like an olive green to a dirty yellow color with a black spot right behind the gills. He has slowly changed color to almost a black over his entire body. what could be causing this. I have never seen him feed and my cichlids usually get all the food before it even hits the bottom no matter how much I feed.. anyone have any idea what could be wrong with him or if this is normal?