This looks like this is probably Elsinoe leaf spot on the leaves and while it seems concerning it isn't something that you need to worry about it. The leaves will fall off soon with the changing weather. Yu can be sure to rake and dispose of them - not in compost- to help manage the overwintering and spread next year. 

Could you provide a photo of what the 'dropped' branches entail? If they broke off, maybe they were cicada-injured if they are a few years old, even if you just planted them, they could have sustained damaged in the field or the nursery. Cicada damaged branches on young trees especially could have snapped in the wind. 

If deer visit the yard, maybe the tree was buck-rubbed in recent weeks and this caused branch damage? When deer reach the rut season they rub their antlers in tree bark to remove the 'velvet' on them. 

The only diseases causing branch dieback would not cause them to fall off, at least not any time soon, so it's probably another cause, or overlapping issues of physical damage with already-dead wood (over-watering? planting too deep? drought dieback?  etc.) Could you provide information on the planting location, soil type and is it well draining, how often and how long did you supply irrigation? If you could also take a photo of the entire tree (trees) and at the base where the root flare meets the ground, that could help us come to some further suggestions. 

Emily