I stumbled upon this thread and thought I'd share some thoughts. It's interesting that you've noticed a drop in pH when your AC kicks on. HVAC systems can sometimes affect the pH of your water due to condensation and air circulation. Using a CO2 scrubber could potentially help maintain a stable pH level, but it's always good to do some research and get advice from experts.
I'm new here and just trying to offer some input. If you ever need more tips or guidance, you should check out 24 hour ac repair inTampa. They might have some helpful insights for you. I know this response is a bit late, but hopefully, it can still be useful for others who come across the same question.