I have 4 long fin panda cories. I am noticing that their fins seem to be getting shorter. How can this happen? Is another fish attacking them? I have 2 clown loaches because I had a problem with long snails. I plan to return them but I am still seeing snails. Could they be attacking my cories? I also have guppies, glofish danios and platies. I plan to return the loaches and get 2 more cories once the snails are gone.