Thanks for writing. Does the mold look like a gray/silver/white powdery coating on the leaves? If so, it's powdery mildew --- one of the most common garden diseases. There are fungicides you can use to help keep the powdery mildew from spreading, but most won't treat the affected leaves. Also: It's really helpful to ensure there's good air circulation to help stop the fungus -- so if your shrubs are growing tightly together, I'd prune them if possible.
---Justin, Senior Garden Editor, BHG.com "