A few weeks ago my fingernails were in a terrible state. They were hardly growing and were all split and flaking. I also noticed I had these vertical ridges on some of them. Visible, but I could also feel them, plus my nails generally felt 'rough' too the touch. Looked online to find out what it was and it said 'normal signs of ageing' which as you can imagine, really cheered me up! 
Picked up a tube of nail cream in Tesco for a couple of quid. I work from home and have been keeping it in my desk drawer and rubbing a bit on my nails when I think about it, most days.
OMG a few weeks on and it has transformed my nails. Not only are they growing well, strong, no flaking, but they are smooth to the touch and the vertical ridges have completely disappeared! I hoped they'd help with the flaking etc. but never thought for a moment they'd do anything with the 'normal part of ageing' ridges, but they are gone.
The cream is called Nunale 'Nail Strengthening Cream' and although I don't recall exactly how much I paid for it, it wasn't expensive. So refreshing to find a product that does what it says on the tin, but also has an unexpected beneficial side effect.