Hi Somya,
Motor milestone happens slowly and sitting without support can happen within 9 months, you can also discuss about this to our pediatrician. Proper Nutrition is also important and can be monitored by baby's growth trend curve includes length, weight and head circumference.
For a detailed Dietary counselling and a Personalized diet chart kindly take up the Nutrition consultation.
Link for consultation (virtual and physical) booking- https://www.cloudninecare.com/doctors/ms-haripriya-n2