Have you experienced any extreme heat this summer? Or periods of extended dryness? Unusually hot or dry conditions can prompt a lot of leaf shedding. And they tend to drop old foliage in late summer or early fall anyway.

It's been an unusual year. We get a week or two of really wet and then a week or two of absolutely dry. I know they tend to drop, but this seems fat beyond what we've experienced in the past

If it is absolutely dry, insert a finger into the soil to a depth of 4" or so, to see if the soil requires watering.