The initial salt pour was about 4 months ago and the pool is 5 months old. 26,500 gallons. The chlorine levels keep dropping to near nothing. I've turned the SWG system dial up from 50% to 60, then 70, then 80. I get higher chlorine levels for a few days, then it drops to nothing again. Do I need to add more salt? The SWG level shows a consistent 3300-3400.