Picture of the whole shrub. Keep in mind I did take a lot of the dead flower heads off (clipped very close to the flower as I have read to do) and a lot of the leaves that had these brown marks on them. However, the middle you can see if thinner.

Looks like Cercospora Leaf Spot. Very common. I have an old hydrangea that came with the house and it has it too. It becomes more visible on leaves as summer winds down and fall arrives. There are fungicides that you can use but they can be expensive. It does not kill the plants so I just ket it be. The fungicides will not cure the problem, just help[ control it so try good housekeeping suggestions: replace the mulch with new mulch if you can afford it and the infestation is buggin you; do not do overhead watering; ditto for sprinklers (but I realize not much you can do about this sometimes... I switched to drip irrigation for other reasons though); water only the soil in the early morning hours; separate the shrub from others to increase air flow and make it harder for the fungi to develop; cut off the leaves when they are dried out and dispose of them on the trash, not a compost pile. dispose of other plant debris under the shrub in the same way. I have clay here too and mixed the clay with organic compost. You will probably get new growth each Spring and it will help "fill up" the affected area.

Here is a link that might be useful: Information about leaf spot

This post was edited by luis_pr on Tue, Aug 26, 14 at 20:21