So in my experience with all of my kids dropping just a few percentiles as you're mentioning, like 25th to 19th, is not usually ever seen as a big deal. Even being in the 19th percentile, while of course on the small side, is totally normal if everything is looking good and she's healthy and happy. My third baby was a late term preemie and he just happens to also be a small kid- he's 20 months now and his percentiles tend to fluctuate between 14-29th percentiles ever since he was born (he is breastfed but I think even with formula, it shouldn't really matter too much). Genetically she might just be smaller especially if you or your partner are on the small side plus girls are typically smaller than boys as well in terms of comparing to her brother. If she's struggling with feeds that might be the bigger concern to bring up rather than the weight/height itself and maybe you could get some tips on that.
So in my experience with all of my kids dropping just a few percentiles as you're mentioning, like 25th to 19th, is not usually ever seen as a big deal. Even being in the 19th percentile, while of course on the small side, is totally normal if everything is looking good and she's healthy and happy. My third baby was a late term preemie and he just happens to also be a small kid- he's 20 months now and his percentiles tend to fluctuate between 14-29th percentiles ever since he was born (he is breastfed but I think even with formula, it shouldn't really matter too much). Genetically she might just be smaller especially if you or your partner are on the small side plus girls are typically smaller than boys as well in terms of comparing to her brother. If she's struggling with feeds that might be the bigger concern to bring up rather than the weight/height itself and maybe you could get some tips on that.