Kinda scared something might be wrong. 😫

Anyone have a problem with their 18 month old toddler not gaining weight? My daughter just went to her 18 month old check up and she lost a pound since October from her last check up and hasn’t gained anything. The pediatrician kept having the nurse re weigh her on 4 other scales. She wants me to go back in 3 months to see if she’s gaining or still losing. We don’t understand though she eats sooo much. Has anyone had this problem before?