Constantly fighting to keep my Ca up

[LeanneP]

I have a 90 gallon mixed reef that has been going for over 4 years. In the last few months I have been struggling to keep my Ca above 380. My Mg was low too, but has since become stable again at about 1400. I started adding kalk a month ago which has decreased my dosing but my ca keeps dropping still. I am using C-balance to dose and am dosing them equal. Right now my Ca is 380 and my alk is 8.4 which is fine except that if I just leave it, it will drop to 350 over a period of time. I had the ca to 410 from a water change last week but now it is 380 even though I am dosing. I have read Randy's info but it doesn't say how to get the ca up and keep it there.