You have a fungas infection. This is common with this species. Mix 1/2 cup vinegar (white is have it) with 6 oz of water and 1/2 teaspoon of sugar. Mist your Azaleas, do not spray a large area, mist it. Do this at sundaow, it will kill the fungas while the plant is partially dormant. Repeat the procedure every night for at least a week. The Azaleas will love it, the fungas will die. -Birdy