2 more links:
http://www.fishprofiles.com/files/profiles/d100011.htm.'
http://www.aquatic-hobbyist.com/prof...olumnaris.html
Cottonmouth is caused by a bacteria. I believe a stressed fish is more prone to any type of illness. The stress could be from a number of things, including poor water quality or pH swings.
What is your water change schedule, how often and how much? Also, how often do you feed? And, what size tank and what all fish are in it?