Brad,
I tried Lynozyme when it first came out. I started developing so many cases of mouth rot I stopped. Never had the trouble afterwards. At least two of my friends in different parts of the world independently told me the same story.. Coincidence? I hope so.
As to competitive exclusion, there is more than one train of thought on this. Read this for more info
http://www.koiquest.co.uk/CE.htm
B.Scott