Help, Damsel sick, white filament fuz on mouth

[justdiving]

This fish has never had a problem before. Today he wouldn't eat, and when I looked he had like white fine wiskers on his mouth. Not ich filimant type maybe an 1/8 long.

How do I fix him? What is it, will my clowns and others get this? I haven't added anything to the tank recently.

Thanks much