Hi, Carole: This could be any number of things, or even a combination, but it sounds like powdery mildew is a good place to start. Go to "Gardening" above and click on "Pests and Diseases Library." Find "Powdery Mildew" and follow the instructions there. While you're there, check out other diseases and see if any of the photos more closely resemble what is happening to your plant. In general, though, clean off or remove the bad leaves, make sure your plant has good air circulation, don't overwater (although brown edges without the white spots might mean underwatering), and put down a thin layer of mulch below the plant to cover up any residual nasties that may be lying in the soil and potentially become harmfully airborne again.
Hi, Carole: This could be any number of things, or even a combination, but it sounds like powdery mildew is a good place to start. Go to "Gardening" above and click on "Pests and Diseases Library." Find "Powdery Mildew" and follow the instructions there. While you're there, check out other diseases and see if any of the photos more closely resemble what is happening to your plant. In general, though, clean off or remove the bad leaves, make sure your plant has good air circulation, don't overwater (although brown edges without the white spots might mean underwatering), and put down a thin layer of mulch below the plant to cover up any residual nasties that may be lying in the soil and potentially become harmfully airborne again.