my son is 31 and he is autistic non verbal, he is in a group home last year i noticed 1 of his finger nails came off, than a few months later it seemed little by little his finger nails started looking weird but not all of them, now when i try to cut his fingernails that are normal looking he crys, and i just noticed it looks like the top layer of his fingernails have been actually clipped off!! What could cause this when my son has never had this and his 3 housemates dont have it either.