baby growing slowly?

Sydney • Kennedy Blake / 10-26-17 / 9lbs1oz ❤️
So I'm worrying like crazy. Is it normal for my little girl to not be growing as quickly as she should be? Last Friday she measured at 15 weeks but I should have been 16 weeks. I went back yesterday, Saturday, and she measured at 15w3d even though I should have been 17w1d. Is she still okay?