Suggest Remedy For Discolored And Brittle Nails

My fingernails have taken a turn for the worst the last several months. Thet grow very slowly and eventually one or two will break. Part of the nails, some not all, have a white portion. I have been taking B vitamins and Biotin because of a thinning hair problem but that has reversed and I m happy with that but cannot seem to solve my nail problem.