Ask-a-Dave's-Gardener: Sick Witch hazel, 4 by Timbasky

Timbasky wrote:
My witch hazel has been growing and healthy for several years. There is always some little sprouts growing at the base which I prune back while they are still small. This year, however, the sprouts are coming up with red leaves instead of the usual green. Can anyone tell me why this is happening? Also, it looks like there is some kind of disease affecting the leaves. It’s happening most heavily on the side in the most shade. In the last picture you can see the healthy side is also beginning to get spots. What is this disease and what can I do to help my witch hazel?