I have a 20 gallon tank, with 5 guppies and 6 cory cats. 2 bronze and 2 peppered. Filter, air supplier, sand, fake plant decor and a few other small things. The ammonia is 0.50, ph is 7.2 and nitate 5.0. Im not sure if this is fin rot or a fungus. One panda's tail is almost gone, the other ones tail ...