Not sure what this is. One of my jurupari is turning black, about 3/4 back on his body (right where the anal fin starts). I can still see the pattern...what it looks like more than anything is frostbite which of course it's not. Almost black on one side, on the other side it's just a shade darker. The fish seems 100% healthy, acts normal, eats, swims around as usual. Anybody ever see this?