Could be the work of the sunflower moth caterpillar (Homoeosoma electellum)

Must agree with the above. We had so much rain this year and the Echinaceas are only starting to perform now that the rain has stopped. Thought we were going to lose quite a few before then. I must say the garden center Manager did a good job of 'up-selling' the fertilizers to you. I agree with Echinaceamaniac about the MG, and will add that the addition of compost to the soil should have been sufficient to start your plant off in the right direction. There was no need to buy fertilizer unless you knew that your soil was deficient, and from all indications, that was not the case since you say that all other plants in the same bed are doing fine. I would urge you to google the "ironate", do some reading, and then see if you wish to continue using it or dispose of it properly. I hope your plants come through and do well the rest of the season for you. :O)

Renee, Thank you so much!! I had spent endless hours trying to find out what is causing this problem.. I looked up your suggestion and it fits to a tee, even the time the adult weevils are out. That explains why my early blooming coneflowers dont have any problems.. I just now have to figure out a way to control them next year. Possibly cutting back all my coneflowers and sunflowers and burning the clippings may help.. I am just glad to finally know what is causing this disaster.. Thanks again, Amy

Echinacea/coneflowers generally do well in healthy soil without much help from humans. My soil is organic (thanks Mom/Dad!!) sandy loam that's slightly acidic. Coneflowers have thrived in these conditions since I grew them from seed 10+ years ago. I do nothing to/for them. It's a bit difficult to comment on your issues since you don't post your location. I'm in Zone 6a in Southern New England and my soil is generally slightly acidic sandy loam. My parents practiced organic gardening 40 years before I moved back here so I know the soil will sustain most perennials with little help from me. Properly planted so they have the opportunity to establish root systems, most perennials thrive in my garden. Your Echinacea/coneflowers are stressed for some reason which presents you with the challenge of discovering why. Perennials know what to do to thrive when given the conditions (i.e., soil, water) they require. Did you tease the roots loose when removing them from the nursery pots? Were the planting holes large enough to allow the plants to send roots down into the soil? Does your soil need amending based on your location? No criticism intended, chemicals are generally not good solutions aside from $$ cost as well as environmental considerations. Hope your coneflowers recover & thrive.