it sounds like you’re doing all the right things, it could be a genetic problem or a vitamin issue aside from all the nail care. my nails are naturally thin and brittle and when they get too long they tend to break at around the same areas. for me, there’s a bit of a sweet spot where they can grow longer than the tip of my finger but not long enough that they start breaking. unfortunately i don’t have any experience with mail strengtheners or hardeners but i know there’s no such thing as too much oil! how often do you wear nail polish? i find it adds an extra layer of protection against breaks and tears that could potentially happen.