I believe the commercial guys use calcium nitrate. I'm sure they don't use what your wife takes. It's probably not soluable enough and would just set on the skin. It probably won't hurt anything.

I don't see how calcium will help with your fungus problem. You should describe, or better, submit photos of the disease and maybe we can suggest the fungicide you might use.

Calcium is only helpful for certain summer fruit rots and storage disorders of apples like bitter pit and corking. The rots are circular black areas that eat into the flesh.

I was thinking of Ca for storage disorders. Sorry, next time I'll read the question better instead of assuming.

For fungus you'll need a fungicide.