I have scores of azaleas (different colors) - perhaps 60+ years old - and have noticed many, many of them have some kind of fungus on them which appears to be killing the branches, and sometimes the entire plant. Some plants are 8 ft high. I just became aware of this in last couple of months (it may have been existence long before), and seems to be spreading. Both sun and shade. No pesticides or fertilizers have been used. Need to know what kind of treatment I need to do. I'm attaching a photo. Thanks.