I think I lost my way a bit. Somehow ph in my tank is really unstable.
Initially I thought its due to CO2
also stopped dosing ferts.
Doing by-weekly 30% water change.
Changed filter sponges, also did vacuum the bottom of the tank.
Still its going low next day post water change.
What can it be changing my tank PH? Ammonia/nitrite/nitrate are in control.