Did English ever have a formal version of “you”?
Second person used to be:Singular----|----Plural   Thou      Ye, You

   Thee      You

   Thine     Yours

   Thy       Your

Which correspond to the nominative, objective, and possessive cases accordingly.By the way, the "Ye" is not related to the "Ye" in store signs that say "Ye Olde...". Y was sometimes used by typographers instead of the Old English letter Þ(Thorn),  which makes a "Th" sound, so those store signs should be pronounced as "The Old..."The usage of "You" instead of "Thou" began in the 14th century. It was originally used in token of respect when addressing a superior, and eventually began to be used when addressing equals.EDIT: Removed part about "you all", because some things I said were wrong and others I will have to look up.