Check out this advice for weak nails... hope it helps!

My nails have never been healthy.  They wouldn't grow out, they peeled, they chipped, and were unhealthy overall. That was before I found the Perfect Formula Strengthen & Seal Sheer Pink Gel Coat.   This gel coat creates a thick, protein-rich coating that helps strengthen, seal, and protect natural nails so they grow more beautifully. And, the sheer pink color adds a rosy glow that complements every skin tone.  I make sure that I remove and reapply once a week as this is a treatment.  You want to have this be the first thing to touch your nails and works wonderfully as a base coat.  After using this for 1 month, I had long, strong nails that looked beautiful and were healthy!  I go through this stuff like crazy and I think it is well worth the price, time, and effort.  This is available at most beauty supply stores.

I hope this helps! 

This isn't a beauty remedy, but a diet one: JELLO. It helps with both nail and hair problems (also recommended for soft tissue injuries)

I found a cure that worked for me. I bought a big bag of whole almonds at the holidays and never used them.  I wasn't going to throw them out so I started to eat about 1/4 cup a day. There are tons of articles out there telling all of us that nuts are good for us. Now I know it's true (for me anyway). I don't know how long if was before I noticed my nails are stronger, not splitting horizontally, and growing. I started this in January and it's only mid March so it didn't take to long. Give it a try. It can't hurt you unless you're alergic to nuts.