Get those other test kits and test all your params.
Start a log for your tank. PM me with your e-mail if you want a copy of my Excel spreadsheet.
Corals need fish poop, or expensive additives.
My thoughts on params;
Alk 8-8.5
Cal 400-420
Mag 1350
Nitrates 1-10 Max. 5 is good. Mine is 0
Phosphates 0.03. Mine fluctuates between 0.00 and 0.002
The balance between NO3 and PO4 is key to coral success, so read about it.
The other key is stability. As Frogger wrote, when your Alk drops, so does your Ca.
Get kits, test 2-3 days in a row to find what is being used, then calculate what your tank needs daily.
Use the online calculator if you can find your product on the list
http://reef.diesyst.com/chemcalc/chemcalc.html
For now, get some stuff from J&L and balance your tank using the online calculator. Get the simple to use stuff to start with EI: liquids or easy to measure powders. Once you get a grip on that I'll teach you about the home-made powders.
I'll tell you about how to use baking soda, and I'm selling calcium in bulk.
But this will come after you understand the whole process.