One of the biggest problems I see people having with their chemistry is balance. The levels of the big 3 (alk, ca, and mg) are all dependent on each other and need to be in balance. In other words, dosing carbonate will not only change alk, but will affect ca and mg.
The take away here, is it is important to always dose equal amounts of two part. These are formulated to replace exactly what the corals are consuming, and the ratio that corals consume alk/ca is consistent, meaning it does not change tank to tank or coral to coral.
If indeed a drop in alk is consumption by the coral, then they have consumed an equivalent proportion of ca as well. Alot of people will dose each part differently to try to acquire the "perfect" parameter. Instead of doing so, they throw their tank chemistry out of whack and struggle to keep things where they should be.
As such, I only test alk and dose equal amounts of two part accordingly to keep the alk stable. The ca will fall in line. Every two months or so, I check the mag, but that is almost always replenished and stable due to water changes.