Hello! 

Looks like you've got cherry leaf spot, a very common problem on tart cherries in Michigan, especially this year. This bulletin has cultural and other practices for managing this disease at the end of this season and for the future: 

https://extension.umn.edu/plant-diseases/cherry-leaf-spot

It also looks like the tree has an iron deficiency, based on the pattern of the coloring on the leaves. This is mainly impacted by the pH of the soil as too high of pH prevents the iron present in the soil from being taken up by the tree. Was your yard ever excavated which would cause the tree to be planted into subsoil (C horizon soil)? 

Here is a nice article about soil pH and the effect on nutrient availability and possible amendments: 

https://www.canr.msu.edu/news/making_the_most_out_of_your_soil_test_ph_factsheet_now_available#:~:text=Lowering%20soil%20pH,using%20any%20of%20these%20products.

To quote the article on lowering ph: "If the soil pH is too high (alkaline), it can be adjusted by applying sulfur to the soil. Products commonly available include elemental or ground sulfur, iron sulfate and aluminum sulfate. When needed, most plants will benefit from using any of these products."