Dont panic! Babies don't always stay exactly on their centile, they grow in fits and starts, and being slightly off a centile could be completely fine. A sudden drop crossing two centile lines or a steady slow drop in weight over the course of a month or so would be cause for concern but a slight drop would just be a "lets wait and see what it's like next time" situation. Are you getting her weighed again in about a week?
Is there a reason why you know how much she put on in just one week? Usually (unless there are other symptoms of a problem such as difficulty feeding/attaching, or nipple pain) you wouldn't want to weigh a healthy baby more frequently than every 2 weeks. This is because if you weigh them too frequently you will see occasional drops in weight and then this freaks mum out (as you have experienced) but over a longer period such as two weeks or more baby will drop a bit here and gain some extra there and it evens out to show a more general trend in the right direction. Centile lines are indicators only, not an exact science.
Do you have any other reasons to suspect your baby isn't healthy and getting the food she needs?
P.S They wont force you to do anything while your daughter is healthy and happy, it's your decision how to proceed and they will try to help you solve any potential problems before they get too serious.
