Just curious, have you tken some new ASW and mixed it up to 35 PPT (SG = 1.026 at 80 F) and tested it? IO will come out at 8.2 when freshly made with Ro when mixed correctly to full-strength seawater.
You kits are suspect, do you have access to a clean and in-calibration pH meter? Personally, I would not recommend any changes until you get confirmation from a reliable source, making bi potentially tank-crashing changes (adding vinegar) based on your test kit is not a safe way to treat the tank. Confirm your test values as suggested earlier before making any changes other than water changes. If water changes did not affect your test results, then your test kit is most likely off (as the water changes should make some difference in the pH, even if only temporarily)...
Good luck, HTH.
BTW, do you does kalkwasser?