The leaves of my hydrangea are covered with large black spots. Tried So.AG liquid flowable fungicide. No help
Have tried fungicide to no avail. Changed soil of one and still came back
Certified GKH Gardening Expert
This appears to be more of a bacterial blight! Sometimes Copper based fungicides can help here, but usually you will have to start fresh. New container, new soil, new plant.
Anything that you reuse will be infected unless it is thoroughly sterilized.
This article will give you more information on the proper care of hydrangeas to prevent future issues: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm