I have been baffled by this. My pool prior to June 19th was testing right at 7.4 ppm for the pH and prior to June 1 the TA was 90. I just got back from vacation on the 18th...and now since the 19th my pH has been pushing toward 7.6...colors don't quite match up...but it seems to match more closely to 7.5, but darker...but not quite the same color as 7.6 on my tester. And my TA jumped all the way to 140ppm.
I shocked my pool before I left on June 7...put in two gallons took it to 16 ppm...which with my CYA at or just above 40 ppm was shock value. Pool did not and still doesn't have any algae problems...and appears to hold FC very well.
Could these TA and pH numbers be rising because I had my clear solar cover on all that time, and only ran pump 6 hours per day instead of 12 as I normally do while the temperature was in the 90s most of the time and we got at least an inch and a half of rain. Would the water temp rising for about 78 to 94 during that time cause the issue. When I came back I had 1 ppm of FC left and tested for and recored no CCs...