My vine maple is mad at me and I'm not sure why....

In the spring, (this was a wet wet spring, Pacific NW region - near Portland, OR), I surface-fed my precious acer circinatum some fancy/over-priced 10-4-8 "slow release" with micro-nutrients fertilizer from the local garden center. And the maple and I had a lovely spring/summer!

The maple lives on the north (more shaded) side of the yard, receiving direct sunlight on only 20% of its leaves (taller parts of the tree) for approx 3 months.

It looked fine and happy until about a month ago, (early August?).

Now, starting with the upper leaves, they are turning dark brown/black, curling a bit and cursing me for some reason.

The maple has had adequate moisture/drainage, though the surrounding "soils" are an awful clay and 3/4" rock mix.

The tree was planted 3-4 years ago within 24" of a French Drain system with a hole 2x it's rootball diameter so I assume excess ground water is not a problem (though I have used an overhead sprinkler system after sundown during the 2-3 hot/dry months).

From what I've read online, there are a myriad of culprits in the late-summer demise of my precious vine maple's leaves, but I was hoping you might give a simple and consoling answer, i.e. "no worries my friend, just wait til next year, or just add a little of brand-X to the leaves or ground."

I'll attach photos if needed, (haven't found the "how to" on adding photos for this site yet....

(for lack of photo, just envision maple leaves becoming dark brown/black from leaf center, and other "newly" "infected?" leaves with black spotting, soon to turn black and curl.

Thanks for reading. I will appreciate any input you can offer.