Treat the quarantine tank for columnaris with the cories in the tank to prevent it from being introduced into your main tank.
You'll have to rinse the heck out of it after you bleach it. Rinse until you can't smell even the slightest hint of bleach. Then rinse one more time. You'll want to bleach after treatment, no sense in treating the tank after.
So plop them back in, and then treat. If you lose all the fish, then bleach the tank and start again. unless your talking Quarantine tank then bleach after every treatment/use.
+1. Every time I disinfect, I always follow it up with Prime.Also don't just rinse and rinse. Use a dechlorinated product, such as seachem prime. It removes chlorine which is what bleach is.(for the most part)