Do NOT blindly continue a prednisone taper when your flare symptoms are reappearing! That’s a waste of your time and your doctor’s time, as you’ll just go back into a full-blown-flare by continuing.
Do go back to your last safe dosage on prednsione, and stay there until your doctor adjusts your maintenance meds. I’d max out the mesalamines, 4,800mgs a day of oral mesalamine and a 4,000mg a day mesalamine retention-enema. If that is not enough then you likely need the imuran.