Answer: There are many different possible causes for your tree to look as though it is drying out. Unfortunately it is very difficult to diagnose long distance because it could be several different insects, different diseases, or even a root problem or an environmental problem. Since the affected ones are planted closest to your steps, I wonder if you used salt to deice the steps? If so, the salt may have runoff into the soil and is causing the symptoms. Wish I could offer more help.
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