This tree does NOT like transplanting at all. It also requires good soil drainage. Plenty of sunlight is a must but they can survive in less than full sun conditions. Also, the less sunlight a site receives, the colder and wetter the soil might be.

You need to do better than 'guess' at the drainage situation.

Yes. I have one and it is not shedding at all. It gets full sun (or very nearly so) and is not only in a well drained raised bed, but is on a slope too. My bet is the same as rhizo's: either not enough sun or poor drainage. Since it seems certain you're going to lose them where they are, I would personally attempt to transplant them. Since you just set them out in the spring, the roots shouldn't have penetrated into the native soil too much. Give the root ball two or three inches all around the original as you dig, just to be sure.

Another thought: Is it possible you planted them too deeply? Be sure to scrape back any soil that was placed over the top of the root ball. I'd pull excess mulch back a bit too. Can't hurt.

And one more thought: Since the plants are next to a wall, is it possible they are up under the eaves of the building and are not getting enough rain?

I agree about donnabasket's point about these trees being planted too deeply!!! Have a look, especially if you have a clay-based soil; you may even need to elevate them slightly above grade on the berm.

Did you buy these trees in containers or B&B?