Water perimeter silliness

[spit.fire]

I've been testing and dosing daily in an attempt to get things right but can't figure out what is causing weird levels and consumption

Cal: 570
Mag 1400
Kh: 7

Calcium won't go down
Magnesium drops by 100ppm a day
Kh stays the same

It's not the test kits either, I double check everything with 2 different saki feet kits and Hanna testers

Any ideas on what could cause this?

Tank is 55g tsv and almost all sps with a few pieces of Lps

Only 2 fish in the tank