Sick wolfish :-(

[Metalthrashingmad]

Hi

My high fin wolf fish has developed a small growth on the underside of its mouth and has become very docile and is not eating well.

all water permaters are normal but I have just done a water change and added salt. Any idea what the problem is and what I can do?

here are some pictures of the fish and growth:

Thanks in advance for any advice.

Cheers, Matt