I hate to break it to you but those white marks on nails are not caused by an excess of calcium or a deficiency of zinc but most likely from a minor injury while the nail is growing!
The medical name for those white spots is called leukonychia which can also be caused by some medical conditions (but is quite rare). By the time those spots show up on your nail, you have probably already forgotten that you might have hit that nail. In some cases, the spots could be a sign of an allergic reaction to the nail polish but the majority of the time they are pretty harmless.
There are foods that can help your nails grow and stay strong though...
Biotin is a B vitamin that can eliminate the brittleness of fragile nails and calcium can also be beneficial for nail growth according to the American Osteopathic College of Dermatology. Here are some great foods that are rich in biotin:
Almonds & Walnuts
Strawberries & Raspberries
Onions, Cucumbers, and Cauliflower