I does sound fungal, but to be honest you would probably have a better chance of hitting the weekly lottery than getting a fungal infection. So, I would assume bacterial. Be careful not to treat with any copper based mediacations or with malechite green during a bacterial infection.
Actually, from what you are describing, I would suggest you be extremely patient and watch your fish very carefully. Only medicate as a very very last option. Perhaps feed medicated flake. If everything is healthy, I bet this runs its course and goes away on its own. If you have a quarintine tank, then isolating this fish would be a great idea.
"Looking in windows, knocking on doors, they need to take seven and they might take yours."