It looks to me like the petals are mostly gone, instead of not opening. I can't tell for sure from your photos, but two things to look for are aster yellows:
and eriophyid mites:
Thanks for your quick response Dennis.
I found a tag by plant and they are Rudbeckia Goldstein. Flowers have 14 petals. Does this change your answer?
Yes- this would make sense that Rudbeckia would bloom a bit later than echinacea, depending on type and light they receive. The same is occurring in my garden. You should know soon!
Thanks Rebecca and Dennis