This is what the Ohio State University Cooperative Extension has to say about River Birch: "Recently, this tree has been heavily planted in Ohio's landscapes. All birch trees require acidic soil and are prone to developing an iron deficiency in alkaline soil regions. There is no practical control for the iron deficiency but to properly site this tree. Note that the natural range includes the acid soil regions of Ohio."
If you have alkaline soil your tree may have developed an iron chlorosis over the years that is now affecting the tree's overall health. Consult with Dayton's City Arborist for advice about your tree. Good luck.