First of all, as everyone else has stated already, anyone who tries to diagnose a problem from a forum post is probably not the wisest...
But in the interest of an academic discussion...
There are dietary deficiencies that can cause nail findings as the Cap'n stated. *But* these are rare in developed nations unless you're on a particularly unusual diet or an alcoholic. Frequently nail findings are associated with diseases. Nail infections (like fugal aka onychomycosis) are common in the general population and especially prevalent in people with significant disease burden such as Diabetes, immune compromise, etc etc. Psoriasis is notorious for causing nail findings, you can also google things like Beaus lines, Mees lines, Meuhrcke's nails just to look.
But yeah, go see your doctor to address your concern because only they can actually look at your nails, hear your medical history, properly diagnose them, and offer you a plan.