IMO, columnaris is a tricky thing and it varies from fish to fish. The columnaris I've had to go against looked like finrot, but then quickly ate down to the flesh and then moved from there. Then it went septic and started killing my fish from the inside out. It was not pretty >.< . Given the sores and stuff, I'm still going to stick to columnaris. However, I'm not exactly an expert. I would go talk to OldFishLady and ask her to come look at this.
In the mean time, I would use precaution and lower your tank temps to 76*s or a wee bit lower to slow the process down. Add either aq salt or epsom salt *if you have live plants in your tank, go with epsom salt*, 1 tsp per gallon at the moment. I don't know which marycyn works against columnaris; I've sort of forgotten.... but if it really is columnairs, I would use kanaplex if at all possible. And, I know I already asked this (I hope I am not being a bother), but could you please take a few minutes to fill out the questions I posted? It would be a huge help and would make things a lot easier. :)