Ryan,
TB is common in Rams. There are a few diseases that show erratic fish movement in fish. What are the symptoms yours shows?
Cillana,
There are so many little things that can happen to fish. I have had a danio with knifeback for years. It could be a giil crab, or a worm. I have also had problems with fish losing an eye. This could be a parasite(Cercaria?).
Some bacterias and parasites are always in the water. When a fish gets stressed due to whatever reasons such as High nitrates, its immune system is less, in turn, it is more suseptable to a infection or disease.
Your cory I am not sure what it could have been. Does it head stand?
Your tetra could have a Gill copepod(crab) like my danio. Not positive, however