My sad Japanese umbrella tree
The tree looks like it is declining and may not recover. This is a beautiful tree but is very hard to establish it. Based on your photos this looks like the issue. You did not mention how old it is and when you planed it. Usually when trees decline the first year of planting it s due to too much moisture, not enough, excessive mulch, poor drainage, planting too deeply, etc. Here is our publication on these types of problems http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/TreesandShrubs/...
We referenced the Manual of Woody Landscape Plants by Michael Dirr.
The hardiness zones are 5-7 but is not as propsperous in Zone 7 as further North. Also, It prefers rich moist, acid soils and sunny open locations. Late afternoon shade is good in hot areas. Protection from wind is desirable and this tree needs careful siting. At this point there is not much you can do. If you have a guarantee you may want to take advantage of it. You may want to
select another species of plant.