I don't think yoy have anything to worry about. My dd3 who will be 4 in 2.5 months is only 15kg she was born 4.155kg at 12 months she hadn't broken 8kg. She was abot 10 kg at 2. She is a perfectly happy growing developing little girl.
I myself am not concerned. She is so happy and healthy and developing beautifuly, she's just little. I just wanted to have the back up in my mind if became a discussion to know it's all good.
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