Thank you for contacting Ask Extension. 

Because you did not include any pictures, I will address this issue in general and cannot be specific since I do not know what the trees look like. 

There are many foliar diseases that affect maples. Anthracnose and leaf spot are two examples. Anthracnose is a spring disease and usually occurs when there is cool wet spring weather. It is caused by several fungi. 

Many red maples develop verticillium wilt which can cause the upper part of the tree to die back and leaves become smaller. Many insects are targeting maple trees also. 

The MSU Plant and Pest Diagnostic Lab may provide a more thorough diagnosis and you would learn what treatment is necessary if any. Go to: https://www.canr.msu.edu/pestid/ to learn how to submit pictures and samples. Finally, a certified arborist will be able to assess your trees. Go to: www.treesaregood.org the website of the International Society of Arboriculture to find an arborist in your area.

I am including several publications for reference of all the many issues that can happen with maples.

https://hgic.clemson.edu/factsheet/maple-diseases-insect-pests/

https://extension.psu.edu/maple-diseases

https://www.canr.msu.edu/news/maple_leaf_blister_and_anthracnose_two_foliar_diseases_that_can_appear_on_s

If you want to provide pictures so that we can accurately identify the problem, please contact us back.