My female platy is slightly swollen on her right side, I've also noticed a slight dark shadow in the middle of her abdomen. She is also slightly bigger on her anul area and has white stringy poo. She is otherwise her normal self, eating well and swimming about. Water peramiters are all fine ammonia 0 nitrite 0 nitrate 0. I feed my fish a varied diet small amounts each day. Anybody have any ideas?