Q.Cherry and Pluots falling from trees prematurely
The last two years my trees have dropped a significant amount of fruit early. In addition, the fruit on my cherry trees, Rainier and Bing, has rotted before ripe enough to pick. Last year we got less that a quart bag on trees that were loaded with rotten fruit. What am I doing wrong?

I am wondering if the brown rot fungus is afflicting your trees - I have included a link to an article about brown rot below so you can make a determination. Brown rot looks like this:
https://extension.psu.edu/plants/tree-fruit/news/2012/brown-rot-preharvest-alert/image_galleryzoom
Preventative measures, such as applying a fungicide in the early spring prior to onset of flower buds appear is key.
https://www.gardeningknowhow.com/edible/fruits/peach/brown-rot-fungus.htm