Yes, it is cercospora. There is no "fix" once the plant gets it so you need to eliminate overhead watering and water the soil instead. This does not kill the shrub but it can make it look bad when out of control. It is actually there all the time but in the Spring you just cannot see it. Now that the sun is not as strong, photosynthesis stops enough so you can see the leaf spot. You can also clean up dead leaves and blooms in Fall (put them on the trash) and put new mulch if the infestation gets big. . Feel free to deadhead the leaves that bug you, aesthetically speaking. There are fungicides to control bad infestations (not to cure though) but they are expensive. I have one in front of the house with this issue too. :0(

Suggest you read up on the problem - I've attached a couple of links for you to review but there are others out there as well.

The disease tends to be more cosmetic than not and is often brought home from the nursery, as overhead watering - which encourages the development and spread of the disease - is common in a nursery setting. The plants can outgrow it and it is seldom seen after the first season in many areas. Plants grown in more shade seem to develop it less frequently so moving yours may be one way to address. And areas with high summer humidity are also more prone.

Cercospora leaf spot

Hydrangea diseases