environmental stress. Perhaps it was windy recently? Or extra warm?

Jean,

Thanks for the info.

Having given this some thought, I think you are right. We have had a lot of rain and in addition, one night approached very near freezing here in the Louisville area.

They look like they may have been hit by hail or sleet. It's a possibility.

Hail or sleet would cause holes. This is burning of the leaves whether it be wind or extreme heat/cold.