My nails don't seem particularly weak, i.e. they don't break easily. I can get them to grow quite long. However, they're very soft and flexible. I can push them completely forward. I drink plenty of milk and get lots of calcium/vitamin D. I'm 17, and they've been this way for quite awhile. Any other possible causes, or any suggestions to make them harder? That is, besides nail polish, which doesn't work because no matter what kind I use it just peels off.