PH won't go up!

The alk/dkh tester in the API kit is figured out by counting the drops until it turns yellow. Luna

 

Couldn't have said it better. My pH drops in the winter time due to the house all shut up and no outside air. I run a air pump outside to 4 air stones in the sump plus a 6" vent that blows right over the tank with outside air. This is the only way I can get my pH up and I also run a Kalk reactor.
I believe Oxygen is your problem with pH.

 

Conditions in your water may be causing the buffer to precipitate out of solution.

Perhaps you have a 1/2 bottle of buffer sitting in your sand and rock. If one day your water chemistry has a big bang -- it might be all that buffer going back into solution.

I haven't read all of the posts and apologize if this ground has already been covered.

 

I'm with Luna on the Ca++, except if you have snails. Ca++ is necessary for shell growth if I am not mistaken.