6.1 is incredibly low for sure, maybe a slow drip with a strong pH buffer? Removing CO2 is the only way to raise pH without also raising dKH, but you've got room to raise it a bit.
Sounds more like the primary issue is the high CO2 concentration in the same room as the tank.
This may be a bit out there but short of improving inside/outside circulation, Snake plants (S. trifasciata) and Areca Palms are incredibly efficient plants. If the CO2 levels in your room are really that high I bet those houseplants would grow like wildfire (and make a sizeable dent in the levels) with adequate care.
