my baby late preterm baby birth weight is 2.1 kg now my baby is 2and half month old my baby weight is 3.6 kg is it ok

A. 1400 g is a very good weight gain your child is actually gaining weight like a full term child only so overall if I look at the birth weight and the fact that your child is premature the weight is going very good for your child and the growth seems to be perfectly good