Help with dry, hard, brittle nails!?

I have this problem on my toenails, and to a much lesser extent, my fingernails.





You can see vertical lines running down them (and in the case of my toenails, also horizontal ones). They never used to be like this. I used nail polish remover like once, 4 or so years ago, and my nails have never been the same since.





While my fingernails look generally healthy, and translucent, my toenails are so thick they are nearly opaque from all the lines running up and across them. Grosss.





Anyone know any ways of fixing this problem WITHOUT using nail polish and taking protein/calcium supplements?Help with dry, hard, brittle nails!?
鈻?mix castor oil and olive oil. this serves as nail strengthener