Hi Dave:
Again, providing advice to homeowners who have yard trees that are showing symptom's of decline is rather difficult, if not impossible. It's akin to someone calling their physician over the phone and then asking their physician what's wrong with them because they're not feeling well...
Therefore, I will provide you with my standard reply for 95% of all forest/tree health questions, "Please contact a certified arborist in order to provide you with an on-site evaluation or assessment of your yard tree."
Find a Certified Arborist: http://illinoisarborist.org/services-we-provide/find-an-arborist/