Hi Sheila,

We would like the plant pathologist at UVM take a closer look at these leaves -- she is out of town until the middle/end of the week. 

It would be helpful to see some photos of the underside of some affected leaves and/or if you send along some affected leaves to the Plant Diagnostic Lab, they can take a look at them under the scope, here's instructions/form if you'd like to do that: https://www.uvm.edu/sites/default/files/Extension-Community-Horticulture/PDC_Specimen_Worksheet_fillable_form.pdf

Generally, the leaves look okay considering the challenging season we've had. We have received many reports this year of premature color or shedding of leaves consistent when trees and shrubs are under stress due to this season's excessive moisture.

The rainy weather has also been prime for many plant diseases to appear. 

Purpling/discoloration of leaves can be an indication of a number of issues including sun scorch, mite damage, nutrient deficiency, disease or general plant stress.

Once we have a better sense of what's going on, we can make some recommendations but it looks like your plant is generally healthy and so no need to be overly concerned at this point.