Minor size difference with di/di twins and I can't stop thinking about it

I am 32 weeks with b/g di/di twins. The boy is measuring in the 75% weighing at 4lb 10oz and the girl is at the 37% weighing at exactly 4lbs. My doctor said they will keep an eye on her and do another scan in two weeks. Meanwhile all my baby trackers say that a fetus at 32 weeks normally weigh 4lbs. The ultrasound tech also said that the girl is measuring "normal" and it's the boy who is ahead of his weight. I don't know why my doctor focused attention on it so now I am freaking out.