I ordered some small wild motoros a couple months ago. for the past few weeks (at least) I've noticed the belly of one of the rays tends to be more pink than any of the others and has a wound on its tail toward the base and on the underside that isn't healing. I can see a couple pinhead spots of blood on the wound too. Tank mates include two other motoros that are doing just fine. It looks as if she got roughed up on something, but the tank is barebottom so I don't understand the cause of the wound. could there be some sort of parasite doing this? The wound looks just like she had sandpaper rubbed underneath her tail...