What’s wrong with the one on the left?

Got both as starters from a local nursery. The one on the left has always been much delayed from the right one. Even in different locations. I just came back after two weeks out of town so my mom was just watering but not fertilizing or the extras. I’m also wondering if/how to prune the right. It didn’t have branches near the soil when I left and it looks like two roots sprang out? It was about as tall as the left when I left. I’m a newbie so any advice is appreciated!