This type of Hydrangea (Hydrangea macrophylla or H. serrata - they look nearly identical and both have lacecap varieties) often contracts one or more leaf-spot infections over the course of the spring and summer. Our weather conditions coupled with their moderate vulnerability to those pathogens results in foliage usually becoming lightly or moderately damaged by summer. While a very common occurrence, they usually tolerate the damage just fine and can still photosynthesize enough to survive and flower well.

Intervention with fungicides is impractical at best and ineffective at worst, but you can clip off any badly-damaged leaves if you wish to remove the eyesore. The rest of the leaf is healthy and still able to feed the plant, so avoid removing too many, particularly if it will strip the plant of most of its foliage. Similarly, avoid trimming back stems themselves so you don't remove flower buds, although this is just for aesthetics and in and of itself won't hurt the plant.

Improving air circulation around shrubs can help minimize infection, as can keeping the leaves dry (excepting rain, of course) by not wetting them frequently with irrigation. Hydrangeas do benefit from occasional watering when we have hot, dry spells in summer and autumn, but in those cases the water should be directed only at the soil around the roots. Air circulation can be improved by lessening crowding, so if plants are large, you can thin-out some stems so breezes can better dry the foliage after rain and dew. Removing fallen leaves in late autumn or winter will also help keep airflow at its best.

Some of this browning and distortion is residual damage from cold snaps earlier this spring; the symptoms of this don't always manifest right away. Some reddening can also be a response to infection, as the pigments may provide a bit of an immune-like response to help protect the wounds. It's a normal reaction and one that might be amplified if plants are exposed to lots of direct sun, since the pigments can also serve as a sort of sunscreen.

Oakleaf Hydrangea (Hydrangea quercifolia) tend to be more vulnerable to leaf-spot infections overall than lacecap Hydrangeas. They don't need any different treatment, but may develop more unsightly spotting depending on our weather patterns. They are tolerant of more direct sun and a bit more drought than lacecap Hydrangea, so could be moved if needed to a different spot if this location proves too challenging for them.

Miri

Miri, 

You're welcome.