Answer: The most common cause of browning needles at the top of a pine tree is water stress. Although you planted your trees at the same time, the growing conditions might be slightly different: drainage can differ, as can amount of water the tree receives. You might want to check the soil moisture content for both of the trees. I suspect the tree showing damage will have soil that's much drier or much wetter than the healthy tree.
Best wishes with your trees!
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