We viewed the photos. We do not see clear signs of insect or disease issues. We see some cicada scars on the trunk that may have contributed to some leaf drop but we do not think this is the real reason for the foliage loss. We also see some major pruning to the right trunk. The tree looks thin and weak but we cannot say why.  There may be several reasons for decline such as poor planting techniques, poor drainage, drought, etc. Here are some reasons why plants fail to establish and factors that contribute to this. https://extension.umd.edu/resource/what-causes-trees-and-shrubs-die

You did not mention how you care for the tree and if there are any downspouts dumping water in the root zone. It looks like the tree may be planted too deep and there is a lot of mulch around the trunk. This can cause poor growth, failure to establish, and trunk damage. 

Also, If the plants were balled and burlapped, were the cords removed and burlap cut loose. If a container plant - if rootbound within the container, were the roots teased apart so they could establish into surrounding soil.

Planting too deep - A properly planted tree/shrub flares at the base of the trunk at the soil line where it joins the root system. In some cases, soil is piled up around trunks at the plant nursery. Excess mulch can cause bark deterioration at the soil line and roots can grow into the mulch. 

Look around the base of the trunks and if need be, carefully remove the excess mulch or soil from the circumference of the trunk to the point where the trunk flares out into root growth. Mulch should be no thicker than several inches and away from the base of the stems. Here is information on planting too deeply and planting trees and shrubs https://extension.umd.edu/resource/trees-planted-too-deeply

https://extension.umd.edu/resource/planting-tree-or-shrub

Look for the above issues and check the soil drainage. Water during dry periods. You can scratch the branches and look for green tissue. If you see brown/gray the branches are dead. 

All you can do is prune dead wood and monitor for new growth in the spring. You will most likely have to consider replacement in the spring.

Marian

You are welcome.

Marian