help me figure out how to add calcium and magnesium to DWC

Elemental ppm is better way to communicate it as dosage / concentrations in products varies Minimum 100ppm of Ca from your fertilizer - that is the cumulative amount across all products added. 75 ppm Mg. Less likely to need more of this. These values are not set in stone. if you get 73ppm Mg / 110ppm Ca that's fine too... regardless of where you start, you will need to observe plant over several weeks to make any necessary adjustments. These values assume you are not feeding to much of something that inhibits either Mg or Ca. It also assumes your pH isn't some whacky value. There are free apps that canan convert your gauranteed label info + dose into elemental ppm.