Baby weight gain

I've been breastfeeding my little girl now for 7 weeks and every time health visitor comes to weigh baby she's lower down on the weight graph,they're talking about maybe sending her to pediatrician. She still above the 50th percentile but started on 91st. She's a very alert, very well settled and happy baby but I'm worrying she isn't growing as she should be now due to this. Anyone else in same boat or any advice?x