19 month old doesnt eat much

Hey! My 19 month old daughter has fallen in weight from 25th percentile to under 10th. She barely eats anything and prefers formula. She does not let us spoon feed her. She eats on her own but is very picky. How do I go about encouraging her to eat without pressuring her? She seems to eat okay at daycare. She is active otherwise but is just very lanky. Thanks!