Answer: I would strongly suggest you run some basic soil tests and make sure that your soil is acidic. It must also be well enriched with organic matter. It should also drain well because these plants are sensitive to overwatering, especially in a clay based soil. The plants must not be planted too deeply, their roots will smother. They should be mulched year round with several inches of organic mulch to help keep the soil evenly moist and cool. Watering should be done as needed to keep the soil moist but not sopping wet. Azaleas are not terribly heavy feeders. Your fertilizing should be done based on the results of your soil test. Fertilizer will not compensate for cultural conditions that are poor. Finally, make sure the varieties you are planting are rated reliably hardy for your area.
Lastly, examine the plants often for any sign of foliar distress such as white specklinh, discolored edges or discolored veins. Take a sample to your county extension and have them identify the problem for you and suggest solutions. Sometimes azaleas suffer from a pest or disease problem and will linger for a year or two before giving up. Some of these can be carried from year to year in the soil, so it is important to have an accurate diagnosis.
I hope this helps you troubleshoot.
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