I have now two platys a tetra a swordtail and a minnow in a ten gallon tank. I been having problems with mollies dying and lost one of my platys today. I have noticed that my swordtail and one of my platys have developed a white patch under and on their gills. I'm not sure what to do. I don't want to lose the swordtail. But he isn't acting normal any more. Any good suggestions. Thanks, mike.