Odd, the numbers I gave are what fresh mixed instant ocean should test to. Here are some guidelines, as long as you are in the ranges you are fine. Once you figure out where you want your numbers you want to keep it stable at those numbers.
http://www.reefkeeping.com/issues/2004-05/rhf/index.php
My targets are 420 Cal, 7.5 dkh for alk, and 1300 mag. I use seachem products to maintain my alk. my cal and mag are maintained through water changes.
Do you have a lot of coralline growth, I'm just trying to figure out what is using up all of your cal, mag, and alk? How often do you do water changes?