Hi, I'm suddenly having low ph isues, bad is low 7s, good is 7.8. Calcium 500, Alk 9.9 (Salifert). Don't test Mg, but added some recipe 1. I run make up RO through a homemade Kalk reactor, have a co2 calc reactor, home made 2nd stage. Electronic ph meter, lab grade calibration solutions. Skimmer...