Here is an article that might answer your questions. In the short term you might try a foliar spray that contains chelated iron to help the trees. Any acidic fertilizer like Mir-Acid should do the trick, but those aren't recommended for long term use since they usually contain aluminum sulfate.

I used to live in northern IL and Pin Oak is notorious for doing poorly up there. A good substitute if you ever plant any new trees is Hill's Oak (Quercus ellipsoidalis) and a good substitute for Red Maple is Freeman Maple (Acer x fremanii). I am surprised the River Birch is chlorotic as I have seen many large, healthy specimens growing in the northern parts of IL.

Here is a link that might be useful: Iron Chlorosis

I must assume you have already studied the University of Illinois at Urbana-Champaign article on chlorosis. I only mention it just on the off chance it was overlooked since you did not mention how you ruled out magnesium and zinc deficiencies.