If they show no signs then give them some time and see how they do. The tank needs to be disinfected to kill columnaris. I had to remove everything and bleach the entire tank, gravel, decor, filter, etc. it’s a lot of work. You can keep the fish in the tank and see what happens or you can get aggressive and put them in a quarantine tank. Then break down the tank and disinfect it. Of course, that means cycling all over again unless you have another tank to get some established filter media from to seed the filter. I left my tank dry and empty for a month before I put anything back in it. Columnaris is horrible. I wouldn’t wish it on my worst enemy. If your fish are being eaten away then I have no doubt it is columnaris. One of my fish was fine one night and the next morning half her face was gone and full of columnaris fibers. Horrible!