FS, thanks so much for your dedication in sharing all this with us. I really appreciate it. I'm sorry you've had to go through the experience, but your sharing will help others who find them selves in the same boat.
Having just euth'd a white cloud mtn minnow with what appears to be mycobacterium, I am concerned about the other fish. I'll be keeping an eye on them and returning to this thread to check on your progress as well. I hope the probiotics and all your other approaches help and you have no more sick fish.