If you have alkaline clay soil, it could be that your plants are unable to take up iron. A soil pH test would be useful, in this situation. I use agricultural sulfur to lower soil pH in our blueberry beds. I prefer to base soil additions on test results, as opposed to guesswork. However, you could put down one tablespoon of agricultural sulfur around a few plants, and see if this improves the color of the leaves. It will take about a month for the sulfur to have much effect.

I am also in IN up North & the soil by me has a ph of 7.
You have done the right amending for IN so you are good there. I hope you added some type of fertilizer. Say 12-12 12 or 10-10-10 or perhaps manure. I use 12-12-12 every spring & I am good to go. When I do notice a plant has some yellowing I first make sure I am giving the plants plenty of water if no rain. To help certain plants out I will spray them with a 1tsp of Kelp to a gallon of water. I spray just the foliage & not on a sunny day. I use powdered Kelp I get at the health food store since it is cheapest there.
The Kelp does turn the leaves green again & it also helps my plant multiply quickly even bulbs like Tulips or Dafs.
Other than some fertilizer/nitrogen you seem to have done everything right. Hope this helps. MaMoo