I have a 90 gallon reef tank. I was dosing 24ml a day of esv b ionic. My pH barely breaks 8.0 in the late afternoon. I bought a new lab grade pH probe for my apex and calibrated it. My pH this morning is reading 7.61 I have calibrated it twice. It reads 10.01 when placed in the 10.01 calibration solution and 6.99 in the 7.01 solution. I do not understand what would be making my pH so low. I have my skimmer set up with an airline to the outside of my house. I left the window next to my tank open all night. My first question is what could be making my pH so low? Can I add Kalk to help raise the pH? How do I calculate how much. I tested my alk this morning it is 7.8 using a hanna checker and my calcium is 380 using a salifert kit. My salinity 1.026 using the milwaukee digital refractometer. My alk and calcium are a tad low so I just now changed the 2 part to dose 32ml of each a day spread out every 6 hours.