Calcium issue

I was wondering how do I just add calcium to my res? I have been having trouble getting my girl healthy and I think it is do to a calcium def. I know espson salt can be added so sodium, but what can I add to raise the calcium?

Calcium nitrate, would recommend greenhouse grade as a bare minimum, medicinal grade if it's in the budget and you can locate it. Both greenhouse and medicinal grade will dissolve much easier than field grade, without a doubt in my mind.