Toddler growth fears

My baby girl turns 18 months on January 17th and she hasn’t grown since before she turned 12 months old. She is 30” tall and just over 20 lbs. She eats a balanced diet which includes broccoli, apples, green beans, potatoes, chicken, turkey, cheese, juice, pasta, bread, butter, among other things. I have been giving her a cup of chocolate milk a couple times a week because she won’t drink regular milk. I am afraid of her dropping off the height chart, which she will do if she doesn’t start growing again in the next couple months. She has become shorter than the other babies she knows who are younger than her. I hadn’t thought about it before much because she eats so well, but I started to really think about it the other day while measuring her again. I am putting her on pediasure today, but does anyone else have experience with a toddler who doesn’t seem to want to grow? It scares me that she might have an underlying problem.