hi mate, this is very strange, and you bagged and refloated them, um did they get knocked when you moved them?
also as shela stated have you checked that your heater has not got a crack or split at them seam?
what temp are you at?maybe drop it to 25-26c and see what happen's....as said preform some daily waterchanges's...leave the lights off and hopefully in a few days they will be ok, iam not up on columnaris so would not know the sympton's...
have they eaten at all, can you lay your hands on live feeder shrimp from lfs, just to see what they do with them in the tank,