ulcer on betta

[shellyx]

Hi I, ve noticed a white lump on my bettas gill to me it looks like an ulcer i caught him rubbing it on a plant. It's not ich as it's to big and I, ve had ich before. Any ideas? He's in a 16gallon ammonia 0, nitrite 0, nitrate 5.50% clean every 4days. Your help would be appreciated. Sorry pics are a bit unclear he wouldn't sit still

 

[shellyx]

Here's another kind of look, s like its fungus or rotting?

 

[Fishanatic]

Did you ever vary the diet of you're betta?
I can't see well, but it might be a tumor, an internal parasite or a bacterial infection.

 

[shellyx]

Did you ever vary the diet of you're betta?
I can't see well, but it might be a tumor, an internal parasite or a bacterial infection.

It definitely looks like some sort of ulcer. His diet is varied he eats tetra color disc, brine with garlic and vegis. Not all at once! He's eating well and doing the norm. On closer inspection its silver? Thanks for helping