Based on your photos it looks like the foliage of the dogwood has been affected by a leaf scorch/and possibly powdery mildew, a fungal disease.
Many dogwoods in the area are showing leaf scorch due to our hot dry weather. All you can do is keep the tree well watered during dry periods up until the ground freezes. Make sure mulch is no thicker than several inches and keep away from the trunk of the tree.
Powdery mildew - You may see a powdery white film on the leaves. There is a range of susceptibility among dogwood to powdery mildew. The best recommendation is to plant powdery mildew resistant varieties in the future. Pruning for air circulation may help. You will have to monitor the plant in the future and decide if you want to spray fungicides or horticultural oil products listed for powdery mildew. This disease does not kill the plant but can weaken it. http://extension.umd.edu/hgic/powdery-mildew-trees-and-shrubs