I suspect that the underlying clay is either preventing water from draining away and "drowning" the tree roots, or preventing the tree from rooting deeply enough. I suggest that you select an alternative planting site for the sick tree. Prepare the site by digging deep, at least two spade depths, to break up the clay, over a wide area (to allow for future root expansion) and add a lot of vegetable matter such as compost or dampened peat moss to improve the soil texture. Choose a day when the weather is cool and damp to lift the tree, keeping as much soil on the roots as possible, and replant it in the new site. Loosen and spread out any circled roots as you plant it. Keep it shaded from hot sun and watered, but not soggy, until you see signs of growth. Hopefully there will be time for it to settle-in before winter. I think you need to act fast, while the tree is still green.
