Once my system was stable, all I tested for were the big 3, alk, Ca, and Mg. I also tested PO4.
And once that was stable with the CaRX, all I did was test my PO4 and alk every month to see where I was at.
I must note that I am assuming you are keeping your eye on your temp, pH, and salinity.
To clarify, when we spoke of Ca readings being off at the March meeting, we were only referring to the Hanna Ca meter. There is actually a formula to correct the offset of the reading if you wanted.