Fetal measurements

Tiffany

I had a scan monday and my twin 1 measured 8 weeks 4 days and twin 2 8 weeks 5 days now its thursday i went for my routine scan as normal as i have 2 a week to help my anxiety and twin 1 was measuring 8 weeks 6 which is brill 2 days growth in 3 days but twin 2 was only measuring 8 weeks 6 days thats 1 day growth in 3 days i am abit concerned as i expected to go and be at least 9 week any advise or experience please ?