I've never had this problem before.
Someone once told me that if you wear a lot of nail polish, and constantly, it will change to a shade of yellow. Mine isn't just a shade of yellow. Like I said, it's noticably yellow. >.O Kind of disgusting. Yet, I haven't worn nail polish in a long time.
Anyway, is there a kind of treatment I can treat my nails or any medicine you guys would recommend?