Betta problem

[Horses2011]

Ive had my betta for a couple months now and now all of a sudden he has ben getting a brown fuzzie looking thing on his one pelvic fin but not anywhere else when i get him out of the tank to do the water change it seems to fall off but then the next day its back and worse looking but still falls off. ive been useing marycine and marycine 2 to treat the gram - and gram+ should i put aquarium salt in his bowl to help im lost at what to do he is still verry energetic and very eager to eat and no color loss. if anybody knows what it might be i would appriciate it thanks.

[Oldfishlady]

Welcome to the forum...need some more information....

What size is the tank, how much and how often on the water changes, water temp, filter, live plants, additives, tank mates...how many days have you been using the antibiotics......

Can you post a pic....