This shrub has a fungal infection that produces leaf spots. Overhead watering promotes the development of this disease. The disease cannot be cured but you can to try to minimize the lesions by never watering the leaves. If you have a sprinkler system that hits the shrub, try watering close to sunrise or 6am so the leaves do not remain wet for long periods of time. Other alternatives: water using drip irrigation or soaker hoses. Another thing you ca do is to use clean sanitation practices. That covers things like picking plant debris under the shrub at all times; dispose in the trash of leaves/blooms when the plant goes dormant. In the case of large infestations, you can try to replace the mulch in the Fall (when the plant goes dormant) with new mulch too.

You can cut the worst of the leaves but always leave most of them since leaves produce food for the roots.

You can also use fungicides approved to treat cercospora leaf spot. I control mine with clean sanitation practices and drip irrigation. In some locations, this disease is common starting in mid to late Summer but in other places, it hardly ever comes back so it is not worth buying fungicides.

Here is more info:

https://ugaurbanag.com/cercospora-leaf-spot-on-hydrangea/

Thank you!

Is your climate such that it is going to lose all its leaves soon, anyway? prune if you want to but I wouldn't spend much time.....just clean up really well this autumn.

I like conserving energy....mine!

I hear you. I went weeding yesterday and temperatures in the upper 90s got me sweating so much that the shirt turned a different, darker, shade of blue. Ha! ;o)) And I was out less than an hour.