I just had my male red velvet swordtail die on me and now it seems the female is exhibiting similar signs, but none of my other fish (black lyretail mollies, dalmation mollies, and 3 marigold swordtails). Is it likely the tank the red velvets were in had a form of disease in it? Before he died, he seemed to hover in one spot with whole body being used to maintain against current. Only other thought is that the male marigold was constantly being aggressive towards the male before he died and now the female. Is it possible he injured the male? and is now going to try to kill the female? Or is likely he just can sense that they had something wrong. Any help is appreciated. 
