baby losing weight

My 9 month old daughter is breastfed and she weighed 21.5 at her 9 month check up but since then she has lost weight and only weighs 21.0 is that bad? the reason i know is because i weighed her on a regular bath scale not for babies😂 omg probably shouldn't since different scales makes a difference right ?I'm going to call her pediatrician soon because I'm worried.