My blue betta has a white patch on his body at the base of his dorsal fin. It started out weeks ago the size of a pin-head and is now nearly the size of my pinky nail. I have done courses of Fungus Eliminator, Tetracycline, Ampicillin, and Triple sulfa. NOT at the same time
, but consecutively as each course didn't work. I do regular water changes and use StressCoat and aquarium salt in his water. Patch just keeps getting bigger. He is eating and acting normal. Anyone know what it is and/or what I need to be doing? I have another betta I got at the same time (18 months ago) and his environment is identical to my sick betta, but he is fine. HELP!