I did get a few batches that were very high calcium and eventually had to switch because of that.

I never mix the dry salt mix from the two containers, just mix them in the water. The main reason I don't mix it dry is that I might change the ratio based on if I need more calc or alk. But I also find it stores amd mixes better if you mix them in water. Mix the one with the higher alk first, then add the other.