It's possible that this is a fungus, such as anthracnose.  You can send a sample of your leaves into the campus Plant and Pest Diagnostic lab to confirm the type of fungus.  https://www.canr.msu.edu/pestid/ Please follow the submittal directions, prices vary.

When watering your trees, be careful to water the soil and not the plant.  Splashing water will spread the spores of the fungus.  There isn't much you can do right now, as fungicides are used as preventatives, not curatives.  Your gardens look very clean, continue to keep plant debris cleaned up, sanitize your tools between plants, i.e. pruners, and water the soil not the tree leaves.  Keeping your trees healthy also helps them fight pests and diseases.  If you haven't done a soil test in the last 3 years, consider a soil test and then fertilize according to the recommendations.  https://homesoiltest.msu.edu/