Answer: Based on your description I am not certain what is happening to your Rudbeckia. Browning and drying can be signs of several different problems. It might be a disease such as a fungal or bacterial infection, it could indicate overfertilizing has caused root damage, it could be a sign of over or underwatering, or it could even be a sign that they are rootbound or possibly a sign of accidental herbicide damage. This type of symptom is difficult to diagnose long distance so I would suggest you work with your local county extension and/or professional nursery staff to try to diagnose it and then based on that, decide how to proceed. I'm sorry you are having trouble with them.
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