Answer: There are several possible causes for them to brown, including mechanical injuries such as trunk damage from a weed whacker or a dog urinating on the foliage, disease problems such as fungal infections, and insect problems such as mites. Unfortunately it is very difficult to make this type of diagnosis long distance and by email. I would suggest you work with your local professionally trained nursery staff and/or county extension to obtain a specific diagnosis and then work from there. The Maryland extension system operates an extensive web site and even a telephone line you might try. If it is something that requires a chemical control, they will have the most up to date information on what to use and how/when is best to apply it.
I hope it is nothing too serious.
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