asking

i have a 4 month baby girl. i gave birth to her at around 36weeks weighing 2010g and 47cm. my mum ask me why she is growing too slow compared to my eldest. now she is 6.8kg and 62cm.. she balance her head but in a little time only. she cant even roll over. my mum said that i need to massage her morning and evening. and also she suggested that i need to give her formula milk because my breast milk is that so nutrirous. my question is, do i need to see a pedia regarding to my daughters growth?