Dry skin and chalky, crumbly nails?!

Dry skin and chalky, crumbly nails?

I've noticed recently that the skin on my cheeks is very dry and flaky, I suffer from excema but not generally on my face, so I don't know whether this is related.
Also, my nails feel chalky to the touch, break and crumble very easily and are lined with little ridges.
Could this be a vitamin deficiency of some sort? And if so, what? My diet is fairly good and my hair and the rest of my skin aren't affected.

This is a mineral deficiency. I recommend you drink purified water mixed with mineral water 50/50. This will replace the minerals that are exiting your body continuously.

I suggest that adults and children drink 40 ounces of water per 100 pounds of body weight every day. Realize that exercise, ambient temperature, and state of health affect the water needs of your body.

Also take 500mg of calcium and magnesium twice daily.