FNSIII

We took delivery on our Hot Spring Envoy salt water spa this week. Have only been able to use it once and today when I walk out an open the lid there is a yellow scum like substance arouthe edges. Our PH is sky high (9.0) and we have been adding one cap of Spa Guard PH reducer on the hour for 6 hours with little or no change to the water. What I am afraid of is starting a roller coaster effect of too high...too low...too high again. I didn't want to become a Chemist. I want a place to have a glass of wine and help take care of my back. Any suggestions are appreciated, Frank