That looks fairly normal to me, for a tree that's been in its spot for only a year and that just had a very wet spring. We, too, have wet springs followed by summer heat. Often the heat dries out the leaves that were unhealthy from all the rain. Has the tree had its second flush of growth yet? You may find that it looks a lot better after that.

Make sure it's doing well in terms of moisture, though. Planted right next to that larger tree, with a hedge behind it, the roots of the more established trees/bushes may make moisture less available to it once the dry/hot weather hits. Do a finger-poke test in the soil a few times during the week to see if it needs a deep watering or not. You don't want to assume it's too dry or too wet-- check it until you get a good feel for how it does in this spot, and how much water that area needs in different types of weather.

Also, is it planted at the right depth? You should be able to see the root flare at the surface.

Variegated trees like this one are not very tolerant of afternoon sun and I'd suspect that is the source of the stress and dropping leaves. This is one I'd protect from any afternoon sun if possible. If not possible, then be prepared to experience some foliar distress until the tree becomes fully established........even then, you may still see some scorching and drying/dropping of the foliage in very hot, sunny weather but the tree will continue to releaf to replace.