Question
I live in western NC and for the past 4 years I have had this problem on just the leaves. It blooms beautifully.

Answer
There are two main leaf spots that affect hydrangea.  They both cause brown spots, so you will have to do a little investigation yourself to figure it out.  

The first is Cercospora leaf spot and it causes many small spots.  The spots may eventually coalesce so that large areas are affected.  The second problem is anthracnose.  This disease has larger spots which are sometimes target shaped.  

I suggest you visit the following website because it provides both images of the spots as well as information about the diseases.  http://www.aces.edu/pubs/docs/A/ANR-1212/ANR-1212.pdfhttp://www.aces.edu/pubs/do...

Please let me know if I can be of further assistance.