This tree has not had a lot of problems in the PNW. Little has been reported but there was a fungal (Cladisporium) leaf spot found in the early 60's. In your case, I think it is just that time of year the deciduous trees are loosing their leaves. Your images show necrotic spots mostly on yellowing leaves. Spots range from black to dark brown and some have tan centers surrounded by red halos. The trees will take what they can from the leaves into the limbs, trunks and roots and jettison the rest. In this condition the leaves are susceptible to a lot of opportunistic fungi that can colonize this tissue. The tree will do fine next year. If you are worried you can rake up and dispose of the leaves via a community collection. That will reduce the pressure from overwintering fungi next spring.
PS - I will do a double check of our records and see what problems these trees might have had in the last 60 years. I am not expecting much.

Prof. Pscheidt--Thanks for the information.  That is reassuring. Anne Bridges