Next spring, feed it some fertilizer that is high in phosophorous and that should help. Since it is fall and the leaves will soon be dropping, I wouldn’t worry about the spots. Several of my hydrangeas do the same thing this time of year. You may find next year that the hydrangea needs to be in a place with more sunlight. Morning sun and afternoon shade would be ideal in your zone. Too much shade will cause problems with the leaves and you won’t get as many flowers.
Thanks for writing!