Go ahead and get new filters. Take out the 3" tablet. He was a dumbass to put it in there. You don't want to put tablets in a filter basket, especially a D1, because it filters so fast, and, the chlorine is heading right down through the heater and it will corrode anything in its path. Only use powder chlorine, tablespoon a week, if the spa is set up with an ozonator. Refill the spa, put in some spa metal gone and new filters and go ahead and turn it on. It is probably ok.