my baby birth weight was 4.2kg now after 3month it is 5.5kg n she looks thin is it fine????

A. See your child has game 1300 g in three months so we calculate on the basis of 400 g in a month and this is ideally very good if you go ahead with giving 500 g in a month and it is 200 g less but even if you check as per 400 g this is a decent enough weight gain