Answer: Unfortunately based on your description I am not certain what is happening to your shrubs. Root damage due to excess soil moisture can lead to browning especially at the base of the plant. This can be due to overwatering for example, or the potting mix may have deteriorated over time so it is no longer draining as well as it once did, or there could be a root disease problem. However there are also some pest and foliage disease problems that can cause browning. It is very hard to make this type of diagnosis long distance. I would suggest you work with the retailer where you purchased them and/or your county extension to try to determine what is happening. I'm sorry I can't be more specific for you long distance.
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