Please send us more information such as what is the site conditions, sun versus shade, type of hydrangeas, etc.
Please send us photos of the whole shrub, around the base, and affected flowers and/or foliage. Many plants have been affected by wet soils and poor drainage. They do get some leaf spots and some varieties are more resistant than others. The leaf spots do not kill the plants. The brown flowers could be natural senescence or a fungal issue.