Check the pH of the water used on Ericaceae members like rhododendrons and azaleas. It is a common mistake to use tap water to irrigate these plants (in-ground or containerized) without realizing that many times such tap water can range into pH of 8.0. This makes ericaceous plants unhappy.
Determine all this kind of base/foundational information, and then make choices to advance the health of your plants.
