Coneflowers are a work horse in many gardens including mine, but they aren't completely issue free. Recently one of my coneflower plants began showing deformed flowers with a complete loss of color in the petals. The petals appeared stunted and pale. In some cases the deformed flowers mimic some new interesting variety of coneflower but it's not, these are the signs of aster yellows. Aster yellows is passed on by a pathogen carried by leafhoppers and can be transmitted to many plants, not just coneflowers. The leaf hoppers ingest something called phytoplasm and transmit it from plant to plant when they feed. Coneflowers, asters, coreopsis and several other kinds of plants are all susceptible. 
For more good information on Aster yellow disease visit the Missouri Botanical Garden.