Small build baby at 4 month

Does anyone else's kids have a small build or below the 10th percentile for weight at 4 months old? Both my firstborn and 2nd are born at 2.6kg but elder one was way chubbier back then when he was at 4 months. My girl is 4 months old and still looks like she's 2 months 😂 she's still wearing NB diapers and I'm kinda getting sick and tired of ppl commenting that my baby is so small. Husband is naturally a small build person too. Next development checkup is this coming week and should I be concern for my baby's weight? She's drinking so much milk but seems like not putting on weight 😅but she feels heavy when carried. I'm not worried that much because I know she's healthy but it's just bugging me when ppl comment on her being small , some even mistook her for being 1 month old and got shocked when I told them she's 4 months.