There are times where buds actually stop advancing. I'm never sure what causes it, but they abort part way through the development process. You'll have to keep us posted. The first picture you have reminds me of one that is not continuing to develop, though on the same plant you can have a plant loaded with blossoms that are healthy. I have a couple of older double peonies that do this. The plant is healthy, there are just a couple of these every once in a while. Keep us posted.
