Bacterial and fungal leaf spots are very common on lots of hydrangea varieties, and this looks fairly typical. If TN has had a wet spring, it's often the case that foliar infections on lots of plants will be more widespread, since wet leaf surfaces are easier for pathogen spores to infect. Despite being an eyesore, leaf spot diseases rarely have a significant impact on a shrub's long-term health. We don't recommend the use of a fungicide since they don't always work well (especially if rainy weather interrupts the repeated treatments that will be necessary) and might harm pollinators or other organisms. Fungicides are preventative measures only, meant to protect healthy growth from infection, and cannot cure existing disease nor reverse its damage. The most heavily-spotted leaves can be trimmed off if desired, but otherwise, no intervention is needed. In late autumn when leaves have shed for the winter, they can be raked-up and disposed of to reduce the spore presence for next year.

For the future, questions about gardening for outside of Maryland are best sent to that state's Extension service (Ask Extension lets you select the state for which the question applies), since we are most familiar with Maryland pests, diseases, and growing conditions.

Miri