I had my water tested and was told all the perameters were great. About 2 weeks ago I noticed a bump by the tail of my whiteskirt tetra, this week one has a bump by its mouth. They are 5-6 years old. This has not affected the blackskirt tetras which are the same age in the tank.It is a 60 gallon and I do a partial 1/3rd water change every other week. They are nippy with each other but nothing out of the ordinary. I did just purchase a bacteria treatment from the co op