Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Turn down the CO2, and add a pinch of baking soda to bring the KH up a bit.
In a 29 gallon tank 1 teaspoon of baking soda will raise the KH by 2 degrees. This will help stabilize the pH. If the KH drops again, you may have to keep adding baking soda for a while.
If the CO2 bubble counter keeps changing maybe there is a problem with part of the CO2 equipment.
Good that you have not added fish, yet. Good to get all these bugs worked out before the fish arrive.