Answer: Although it's always tricky trying to diagnose plant problems without seeing them, your description of gray, powdery coating may be a thick infestation of aphids. Use a magnifying glass if you have to, or scrape some of the coating onto a piece of black paper (better contrast). Aphids can be wiped off, and then you can treat the tree with Bioneem or insecticidal soap as directed to keep the critters from returning.
Another possibility is tip blight. This is a disease caused by a bacterium, and it's not uncommon. Here is a link to a page that provides more details about tip blight and how to save your tree from further deterioration:
Kansas State University Dept. of Horticulture bulletin
I hope this helps!
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