When I upgraded to LED's and added a bunch of SPS they took off growth wise. My alk would drop to 4, my calcium to 280 due to the sps draining it out of the tank. This is when I started dosing both calcium and alk with dosing pumps and a controler. It brought my alk back up to 9 and my calcium to 420 and stays there if I dose daily. If I stop dosing they drop, this i assuming is how you know your system needs dosing.
It took me 3 months of daily water tests to fully understand how much to dose of each (cal/alk) daily to maintain. There's a science to it for sure...