What kind of soil are these Digitalis growing in?
The most common fungus problem with Digitalis is Powdery Mildew, but any plant trying to grow in a too wet soil could be suscetible to many problems that are not normal.

Thank you for your response Kimmsr.
The foxgloves are planted in fairly well draining soil, however, it rained pretty much the entire month of June so excessive moisture could be the problem. I have powdery mildew on my garden phlox though and whatever is on my foxgloves doesn't have the same appearance, in that it's not white and isn't necessarily coating the leaves. The stuff on my foxgloves seems to be rotting away the leaves.

Mine are turning a dirty gray and dieing I have been growing them for many years with no problems until now. But this year I have an abundance of them.