Good idea about the nail polish. I was a bit reluctant to purchase that as I have had the "stones" fall off another one I have (a cascade of leaves) and now it looks a bit crappy. I wish I'd known about that trick. Can you see the nail polish at all?
No, apply it thinly, let it dry and then do it again. I did mine 3 times just to be safe. There's no guarantee but I think it help!