Your issue looks a lot like a few trees I have by my house. They were doing good a month ago, then they started looking sick and all the leaves fell off. One just started growing new leaves again, but two others don't appear to be showing signs of life. Those two trees did the same thing last summer though and I thought they might be dead, but they looked fine this spring.
I have no advice other than to say even if they lose all their leaves in mid-summer they could spring back to life next year.