Well, I didn't say it definitely was, GG, but having seen/dealt with aeromonas a couple times more than I'd like to have, I can definitely say that it doesn't start out as a giant hole in the side of the fish. The lesion generally looks very innocuous at the beginning stages, and might escape notice until the point where the hole opens up to the inside of the fish's body. I've only dealt with it in goldfish though, so there was definitely a larger window of time in which to deal with it. With a fish as small as a sword, I think fast and definitive action would be the best bet. However, given the uncertainty of what the issue is currently, the best course of action is to isolate the fish, give it absolutely pristine water, and salt as a precaution in the mean time. If the issue continues to get worse given the absolute best conditions, then you know you have a problem.