I have numerous blooms on my hydrangeas, but they are not fully opening. The tiny buds around the edges are blossoming, but none of the center buds are opening. The bushes get plenty of shade during the daylight hours; perhaps they are getting too much to fully open?
Hydrangea Blooms Not Opening
Certified GKH Gardening Expert
5 hours of sunlight is generally a good amount for flowering.
You could try a boost of Phosphorous to encourage a flowers to open fully.
Bone Meal is a good way to do this.
You may want to do a soil test in the future to make soil corrections.