I would check all your filter outlets and make sure they are well below the water surface. If you have a lot of surface agitation, lower the outlet even more or fill the tank up more. Are you using a co2 drop checker with 4 dkh water and ph solution to measure the co2 levels?

Ph is also very high for me out of the tap. I use a ph controller to drop my levels down to 7.0 which gives me about 30ppm. I also have lots of circulation throughout the tank (two canisters on my 90). Are you running the co2 on a timer or a ph controller? If you want a ph controller, I can trade you a milwaukee unit for one of those tlf reactors.

Not sure why the ph is higher in your tank. Do you have any limestone in there? That would definetely do it.