Yes, they seem to really suffer if I reduce potassium so generally try to stick to my planned dosing even though it seems high. I should test tap water and see if I get any reading on potassium - maybe that will check the test kit is still working.
The drop checker seems to be staying green even when the co2
is off. I need to properly check this on the weekend though. The new drop checker is much easier to read but I'm using the fluval drop checker solution (new bottle) and just have a suspicion that it isn't changing colour much.