Answer: The amount of water a plant receives is only one of the factors that contributes to root rot. Soil drainage makes a big difference in a plant's health and how quickly one spot drains may not hold true for other spots in the garden. This might explain why some of your plants are affected and others are not. Rhodies vary in their resistance to root rot so, unless all the rhodies are the same cultivar, it's not unusual for only a few of many to be susceptible to root rot problems.
Phytophthora is a fungus that is responsible for root rot, but other fungi can compromise the health of rhodies. (Poorly drained soil can also be responsible as roots suffocate in water and are then invaded by rot organisms.)Remove and destroy infected plants and do not replant into the same hole. To avoid root rots, provide good soil drainage, maintain proper nutrition and soil pH, and be sure to purchase healthy, vigorous plants.
Hope this clarifies things for you!
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