The test reagent for PH can give a false elevated PH result when FC (chlorine) is over 10, that is why the PH has to be stable and between 7.2-7.8 before starting a SLAM

As for raising PH, have you tested TA? If the TA is low, you can use Baking Soda, if the TA is "good" you'll want to create aeration (air compressor works too!) and/or use Washing Soda (soda ash) to raise PH instead of paying double for the same thing in PH up (check the chemical ingredients on label)
CH (calcium hardness) = not needed for vinyl, don't add!
That can change in a heartbeat with no chlorine in the water