i had a major die off only my 2 angels survived. everything is running fine and angels look real healthy . today i put a jack dempsey and in a matter of hours its has white on it scales and on the edges of its fins almost looks like its shedding, even on its eye too.wats wrong i want to start adding fish again. but not if this happens all the time. the tanks just has 2 angels in it and they look healthy. wat should i do.