He looks bang on where he should be tbh. They just look to have them anywhere between the 2 dark lines. The measurements aren't 100% reliable so don't get too hung up on them honestly. If the growth continues to go down then they may send you for a scan but honestly looking at your chart you're measuring bang on atm x
I honestly wouldn’t stress, take it with a pinch of salt. My baby has been measuring over the whole time then at my last appointment he was under so I was sent for a scan and turns out he’s completely healthy it’s just never 100% accurate
As long as it's within a weeks range I don't think they worry. Also the tape measure isn't the most accurate. I was measuring 2 weeks behind with the tape, but growth scan said everything was on track. It could even be down to the position of baby at the time. I wouldn't worry too much. But if you are concerned, just check in with your midwife, I'm sure she'd be happy to reassure you, that's what they're here for x