Mina

Worth adding that the stuck-open failure is a lot more common on cheap solenoids and people rarely mention which one they had.

No, you should not be doing anything at two months. Two months is the worst time to change anything, because a new tank is still finding its balance and almost every problem people panic about at that stage resolves on its own by month six.

Adding injection to an unstable tank is how you get an algae outbreak that then gets blamed on the CO2.