My Hydrangea Flowers are not opening

[Boodreaux]

We have five Hydrangeas in our front yard. We put three Endless Summers in last year. We had two older ones, I don't know what kind they are.

When we bought older ones, they were done blooming. We put them in the ground and the next year they had very very few small greenish white blooms, probably because I over pruned them.

The Endless Summer and the older ones have come back full and beautiful this year, and they have large (Silver Dollar) size clusters of buds, but they are opening their flowers just a few at a time. The effect is not very pretty, the individual small flowers are kind of a pinky green.

I may be too impatient, do they take a long time to open fully? Or is there something I am doing wrong?

Any advice would be welcomed.