Joan,
   I checked a lot of different sources regarding the problem you are experiencing with your coneflowers. From that research I would say your coneflowers are suffering from Aster Yellows. Two of its leading symptoms are deformity of the stems and flower buds and chloris of the leaves. Chloris is seen in the sharp contrast between the leaf veins and the leaf surface.
   Aster Yellows is becoming more and more common these days and is caused by a pathogen carried from plant to plant by leaf hoppers. Here is a link to a fact sheet from the University of Illinois Extension discussing Aster Yellows on coneflowers: https://extension.illinois.edu/blogs/garden-scoop/2021-06-26-aster-yellows-coneflower. 
   The sad part of this diagnosis is there is no viable treatment or cure for Aster Yellows. Plants must be removed and destroyed or the pathogen will continue to spread through any healthy coneflowers and other plants in the Aster Family close by.
   The only true confirmation of the disease is through a lab test. If you wish to take that step, here is the address and phone number of your county extension office: 

90 S Broad St
Canfield, Ohio 44406
PH:<personal data hidden>

  They will be happy to assist you with taking, preparing and sending a sample to the OSU Lab for analysis.

   Thank you for your question and I just wish I had better answers for you.

Thank you so much for your quick and informative response!
Sent from my iPhone



Joan,
  One thing to remember is quite often what we see is caused by multiple factors. That's why the lab testing is so valuable.
  Have a great summer.