This looks like the normal progression of age for these flower heads. The petals fade, and the cone centers elongate and eventually lack the yellow pollen rings. At this stage the flowers have been pollenated and seeds are forming.

You can cut off some of the old flowers which may spur some new flowers (which will be fewer and smaller). It's great though to leave some mature heads for songbirds like our yellow goldfinches that love to hang on them and eat the seeds. These perennials can also self seed for more future plants if there is bare, moist ground available, though the colors may not be the same as the hybrids you have planted.

Christine

Thank you, Christine.  To confirm, this doesn’t appear to be any form of fungus.  I’m surprised these are withering and dying so soon.

No, this is normal for coneflowers, which are perennial plants returning each year. Perennials bloom for just a few weeks of their life cycle. Annuals, which die with frost are the ones that bloom for the entire season if they are dead-headed to remove spent flowers so they don't go into seed ripening mode.

For what it's worth, one of my co-workers said that many of the newer varieties of coneflowers, sporting newer colors like red, yellow etc. are not as hardy growers as the native purplish/pink, to the point that some growers pick off flower buds for the first year or so of establishment so that they send energy to their roots and stems as opposed to flower and seed production.

Christine

Thank you, Christine.  This is helpful.  I will likely take to hear your co-worker’s observation and liberally deadhead the languishing flower buds

A good plan.

You are welcome.