Cal-Mag

My plants currently have a Calcium deficiency. Someone advised me to use Cal-Mag to resolve the issues, but the closest store to me that sells Cal-Mag is over 3 hours away.

My question is: Is it possible to use human cal-mag supplement tablets (Found at stores like GNC), dissolve them in water, and give to the plants? If so, what would the dosage be? I believe most of the human tablets are 500mg.

I think some people use epsom salt instead, I think it's like 1 or 2 tsp per. gallon. Someone should be along that knows for sure.

I read somewhere 1 tablespoon per gallon would be fine.