Slow increase on baby’s weight

My baby is 9 months now and her weight has been around 6.5kg for about 2 months now. She’s very active. Has no issue drinking or eating. She has always been 25th percentile since birth. But weight started to fall below 25th percentile which will concern the doctor soon. I’m not too worried as she’s not showing any weakness or so. Or should I be worried that she’s not weighing enough for her age?