Answer: It's really hard to determine the source of the problem without more information. I can make a few suggestions: there are bacterial blight diseases that are ever present and strike when a tree has been weakened by other factors. Japanese maples are more delicate than other maples, and don't fare well in places that are exposed to extreme winds and other damaging weather. The weather has been so strange this year that even if you've planted your trees in a sheltered place, they may not escape damage.
I suggest you have a knowledgable local professional take a look at the scene and suggest the cause, so you can protect your other trees from future problems. Your agricultural extension office (ph# 517-546-3950) can put you in touch with someone who can help. Good luck with your tree!
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