Yeah, I don't want to mislead here. Big fluctuations on Alk are not good. But a change of 1 dKH will not kill your corals (have done that many times with no ill effects). Not sure what type of change you are talking about.
And with Mg, best to raise it only 100 ppm per day. I manually dose Mg every 3 weeks with my water change.
I dose MB7 every 2nd or 3rd day. It adds beneficial bacteria which prevents cyano and works well with your bio pellet reactor to prevent mulm and clumping. Plus it generally makes your water clearer in your tank, with less detritus on your rocks and sand. Here is a link for that.
http://brightwellaquatics.com/produc...robacter7t.php