Answer: It sounds like your azaleas are suffering from fungal leaf spot, but it's really not possible to tell without seeing the plants. Fungal leaf spot tends to attack weakened bushes (it sounds like the other azaleas are strong and vigorous, and have been able to fight off the disease organism). First, send or take a sample to your cooperative extension service (ph# 444-1755) so they can verify the source of the problem. If fungus is the problem, pick up and destroy any fallen leaves to reduce the amount of spores in the area. The extension service may suggest using a copper fungicide to prevent the spread of the disease.
To bring your azalea back to good health, make sure it receives the correct amount of moisture and adequate -- not too much -- fertilizer during the growing season. I hope this helps!
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