Cotton Growth on Clown (Pictures)

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Hi All,

My Clownfish of 5 years has some cotton growth below his lower lip. I first noticed it yesterday. He's been mated with another clown for years. They are both in an established 65 gallon aquarium. All tank parameters are fine, so I won't waste your time.

To be honest, I haven't had to play fish doctor much over the last 5 years with this build, so I'm rusty. I'm guessing this is a bacterial infection. The water quality is fine, so possibly an abrasion caused it? Open to suggestions on a diagnosis and also what to treat with. I appreciate it!

Please refer to the photos. Thanks again!