Refresh is non chlorine shock aka MPS. You must be using trichlor pucks in a floater, generally considered to be something you don't do in a spa, but a couple of manufacturers allow it and some dealers may wrongly recommend it as an "easy" way to maintain your water. I would suggest switching to dichlor after use and shocking with refresh weekly. The very low pH of trichlor and the difficulty of maintaining a correct free chlorine level with a floater are most likely creating your problem.