my baby is 5month 14days now I'm using similac stage 1 becoz I'm not getting sufficient milk. so when should I start similac stage 2 . My father bought stage 2 suddenly so should I use it or should I wait till my daughter cross 6 months. is it compulsory to cross 6months?? My baby birth weight is 1.9kg. now she is 5kgs. can I use stage 2 or continue stage 1 till she completes 6months .??