I'm new to all of this but had my Inground 15000 gal pool replastered about 10 days ago. My PH after refill was/is at 8.0 so I put (too much) Muriatic Acid in to lower it to 7.0. The next day it was 8.0 again. My TA was 80 and now is 40. How can I get my PH to be stable?