Hi, I noticed this strange growth about a week ago on one of my hi fin white skirt tetras . I have been treating the tank with melafix since sunday in hopes of preventing further infection of the open wound/sore/lesion. It is a 29 gallon tank with 3 zebra danios, 3 red eye tetras, 2 small marble mollies, 2 hi fin white skirt tetras and a cherry barb. I did a water test and found ammonia=0ppm, nitrite=0ppm, nitrate=15ppm pH=7.2. My tank is currently at 74 degrees F and I do a 25% water change every 2 weeks.
here is another photo of the fish in question, sorry the photos are not very good.
The growth is about the size of a pea, I have no idea what this could be and how to treat it. Does anyone know what this could be?

here is another photo of the fish in question, sorry the photos are not very good.

The growth is about the size of a pea, I have no idea what this could be and how to treat it. Does anyone know what this could be?