I have a tank with 1 male, 7 female guppies, 1 dward platy, and 3 tetras. I put one of my females in the birthing tank because most of her back tail fin is gone, I don't know which fish did it but I am wondering if it's because I am not feeding the fish enough. Just recently I started feeding them 2x a day instead of once a day. Just about 2 weeks ago I moved them into a 30 gallon. She is a little smaller from the other fish, but I bought her at a reputable fish store. Any suggestions will be so much appreciated. Also what can I do to make her feel better. She is still swimming around and everything.