Azelea plant disease
We viewed your photos. This looks like lace bug damage a sucking insect. This is more an issue on azaleas stressed from the sun. Azaleas grow best in morning sun and afternoon shade.
The least toxic controls are horticultural oil/insecticidal soap. They will only give control if the lower surfaces of the leaves are thoroughly sprayed. Do not spray the above products in hot weather and follow all label directions. Monitor throughout the season. http://extension.umd.edu/hgic/lace-bugs-trees-and-shrubs