Hi Erin,

I too suspect the tree is too wet. Mount Royal doesn't tolerate standing or excessive water. There's not much you can do except hope for drier weather, which in the Twin Cities is supposed to arrive after next week.

Your photos don't show the base of the tree. Mount Royal is a grafted plum, meaning the top has been grafted onto a hardy rootstock that will control how big the tree is. That graft -- which looks like a crooked bump at the base of the trunk -- should be exposed, never buried. If it isn't, scrape soil away from that area so it is exposed.

This page has useful links at the bottom that discuss this variety in more detail:

https://trees.umn.edu/mount-royal-plum-prunus-mount-royal

If you aren't convinced that too much water is the issue, this page has other possible causes:

https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/prunus/

Hope this helps. Good luck.