I had just transferred my female swordtail to my 30 gallon tank after being quarantined for fin rot for the past two months. Today is the 3rd day since then. Tonight I went to feed my fish and she was lying on the bottom of the tank. I finally got her to move and saw she was dragging her tail and that there were black spots all on her lower body (not the fins). I have never seen this before! PLZ HELP!