I have the same question posted on this site but didn't see the answer to the quetion!!!!!! This has been going on for years with me and sometimes the nails will be fine and others all of my nails on both hands will be curved or curved downward. Please post an answer on the web site! Looking forward to seeing one.
fingernail problem
Kate Smith
answered this
Discolored, Loose, Or Abnormally Structured Nails: Do You Need To Be Worried About Your Health?