Hi Aaron, I’m in your neighborhood in fact. I noticed those peach trees chopped down a few weeks ago.
Re: the plums, the most likely issue is plum curculio, all the plums will drop with that worm. I spray Surround clay to deter them. They also can rot badly, you will need several rot sprays. Satsuma is a great plum but I found Santa Rosa did not set fruit reliably at all so I took it out.
My spray regimen is
So I would take a look at it and see what I do. I am happy to chat sometime as well.