I m having a problem with my nails, they have vertical lines and at tip of the nail where the line is, they split. I haven t had a manicure or anything on my nails for two months, but they are so weak, I m thinking I need to have a manicure. Is there a specific vitamin or mineral that I am low in? I eat a very healthy diet, I m 71 years old, 5 2 and weight 130 pounds and take no medicine.