Will Switching From Nan Pro To Lactogen Help My Premature Baby Gain Weight?

Hi doctor my baby is premature she weight 2.3 kg she is in her 3rd month as a mother I don t have sufficient milk to feed baby I was using nan pro to my baby till 2 month now I switched to lactogen because nan is more expensive. Will lactogen help my baby gain weight and there is any issue switching to lactogen please suggest.