Answer: These shrubs, Photinia fraseri, are only considered reliably winter hardy into zone 7 and your zip code places you in the somewhat colder zone 6. Between winter stress and being prone to disease, there may be a combination of factors causing dieback. I would suggest you consult with your retailer and also possibly with your county extension to try to determine what is happening with them and, based on that, how best to proceed. I'm sorry you are having trouble with them.
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