Hello my platy has been hiding recently and I took him out and noticed he has dropsy and has some dark red spots.he has been in my 29 gallon tank for almost 9 months. I have 6 lemon tetras, a bristlenose (I think he sucked some of the platy's slime coat- I suspect he is the cause of a missing corydoras catfish), and a lone three lined Cory (not ideal I know). What is the cause of this? None of the other tank inhabitants have it, so it can't be from deteriorating water conditions. I read it can be from organ failure, could this be the cause?:help2: