Just visited a salt pool which has had the electrolyser turned off for the winter. Last month when I checked the free chlorine was at 6.03 ppm. This time it's 9.82 ppm. No chlorine has been added and the pool temperature is roughly the same at 10 Deg C. Combined chlorine is still low. The pool is on 6 hours per day pump cycle and is kept covered. Any ideas what is going on?