It’s possible that at least some of what you are seeing is leaves affected by anthracnose which is a fungus.  With our wetter start to the spring and summer, this is not unusual.  Anthracnose by itself does not typically cause significant damage to the tree.  See the link below and compare with what you are observing.  However, it may be worth contacting an arborist to evaluate the whole tree health and see it in its environment and see if anything else is also contributing to what you’ve seen over the last couple of years.  Sometimes cities have an arborist that can come out to residents homes, or you could consider hiring one.  Here are some links below for further information.  
https://extension.umn.edu/plant-diseases/anthracnose-trees-and-shrubs
https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional