The last few days my fish in the morning are at the top gasping for air. The CO2 is around 6.5-6.6 and the drop checker is green. I cut back the CO2 and this did not change anything but the PH to 6.7 I changed the drop checker solution and re calibrated my PH monitor . Because of the drop checker reading a constant green. I have not tested the KH. I assume it is still at 5 degrees. Is there something I am missing?