Garden Pests and Diseases: Sickly Gaura, 2 by MiniPonyFarmer

MiniPonyFarmer wrote:
My Cherry Brandy Gaura grows in full sun in raised well amended beds. Over the past 3 years, several have been affected by discolored leaves that feel rough. I have sprayed with antifungal applications without saving any of them. Once they start to become diseased, they never get better. Sometimes, two will be side-by-side in a bed where one is sickly and the other perfectly healthy. Even diseased plants continue to bloom and live. Should I just discard the diseased ones and start over? Or is there something I can treat them with?