Frank wrote:

"looks like a patch of white cotton on the mouth" sounds more like
Flexibacter disease, which is bacterial rather than fungus. You need to
treat the tank with something like Kanamycin or Maracyn Two as they are
not harmfull to your bio-filter. Feeding a medicated food would help a
great deal also, but not Tetra's as flex. disease is resistant.

Thanks for both of your responses. Guess I'll go and get some
anti-bacterial meds. Sure don't want to over use the MG. Will also
pick up medicated food.