Hayward SwimPure Extreme SWG cell replaced October 2020. Recently was reading very low salt numbers on the diagnostic panel. We added salt…and added salt. Decided to test salt with my Taylor kit…6000. Pool store tested also..5400. Replacing some water in the pool now. What would cause such a discrepancy in the salt numbers? Bad cell? I plan to make anther trip to pool store for them to test cell.