The work is a collaboration between my home university and another research group. We first submitted the work to a pretty good journal where I was the second author. But the publisher recommended we submit it to a different/ more suitable journal, and I found out I'm fifth author now. I'm just an undergrad, so I don't want to step on toes before I apply for a PhD.
Edit: The other group made the change. The corresponding prof from the other group was last author earlier but is now first (they are still the corresponding author)