My Black Tetra is in Peril!?

First off my Black Tetra (BT) is 2 years old. About 3 months ago my BT got a tumor. He still ate and nothing seemed wrong. Until another fish attacked him and ripped it off. My BT known as "Gold" started breathing really heavily. His mouth started to swell and then look as though it was falling apart. I separated him from the others and took him to the pet store. They said Mouth Rot. I got meds but its been 4 weeks now and some odd cotton growth is coming out of his badly deteriorating mouth! I have salt and am still doing the meds. Changed the water and he won't eat. Will he survive?HELP!