They are all dry and are white at the tip

It could be just due to dryer weather. Depending on where you live, perhaps with heating on. Some women find that certain soaps can be drying and it may be better to avoid using soap on your breasts when bathing. Some medications may result in drying.

If you can't attribute it to any of those possibilities, and you feel it is getting worse, you may want to see your doctor for a check-up.