Are they in soil that drains well? Have you had heavy rainfall lately? While purple coneflowers will grow in almost any kind of soil, they do need soil that is well-drained and can suffer if they are in slow-draining soil during rainy periods.

Otherwise, I don't think I've ever had pests or diseases bother them, so I'll find and link something that discusses pests and diseases of coneflowers.

I cannot think of anything that would chew on the leaves that then would cause the stems to bend over and droop like that. Weather might have caused it if you had strong wind, heavy rain, hail, etc.

Tony Avent's Discussion of Coneflowers....Read Down to Pest/Diseases Section

I just got my first coneflower flower...and several more blooms. Mine have a few bad spots that could be from insects or hail. We had hail a couple of nights ago. Did you have hail?

Dawn, we have had a decent amount of rain and the soil is pretty sandy. I do try to amend as much as possible with good compost and the soil just seems to suck it up and ask for more. I mulched well this year, since last year was so wet I couldn't keep up with the weeds and only lightly mulched.

I went out this morning and all but the one I photographed have stood back up (they weren't as bent, just flopping. (Last night I did wipe them with an alcohol swabbed cotton pads.)

I pulled the one I photographed and, on closer inspection, it looks like there are several spots around the bent part of the stem that look like bug damage. Hopefully, that is all. I will double check pictures of the diseases mentioned in your article to be sure. I really like the purple coneflowers.

Hazel, aren't they beautiful? We have been so fortunate to not have had hail (knock on wood) and only one stretch of rain that seemed endless. For a day or two, I began to have flashbacks from last summer, lol.

I went back out and found the plants that looked damaged were bent over, so I cut them down to about a foot. Found one that had something(s) in the "elbow" where a leaf was growing out of a stem. I also found an awesome ladybug that was apparently trying to fix the problem. Let her go, then went out this morning to spray with castille soap/water solution...then it started raining, lol. I'll wait for it to stop and see if the sun is going to be bright today before I retreat the plants. (BTW, I found a plant from another part of the garden that looks like it has been affected.) If it's too sunny, I'll try it after then sun starts going down.