Columnaris, fungus, or discoloration?

[Perci]

My male sparkling gourami’s mouth started to turn pale after he spawned. He is seemingly healthy and is very fiercely protecting his little babies but I worry about his mouth. No other fish in the tank is acting strange and his mouth doesn’t look fuzzy, only pale. No other discolored spots on his body and he is eating normally.

Nitrites, nitrates and ammonia are all 0. I have 0 nitrates bc I have a lot of plants in the tank I assume.

 

[Colin_T]

How long has the mouth been like that for?

It's probably a fat lip from fighting or swimming into something. It usually goes away by itself in a week or two.

Columnaris will spread over the face and head within a day or two and the fish die shortly after that. If you haven't added anything to the tank in the 2 weeks before this started, it's unlikely to be Columnaris.