Answer: This plant is generally considered pest and disease free so I have no easy answer to your question. It might be a case of frost damage to the new leaves that is only now becoming apparent, it might be a case of salt damage due to winter icing salts in the soil, it might be accidental chemical exposure such as a weed and feed product. It might be due to aphids, these small soft bodied insects gather at the growth tips and can be washed off with a strong spray of water from the garden hose. If none of these seem to fit, you might want to consult with your county extension and/or your local professionally trained and certified nurseryman to see if they can diagnose it more specifically and then based on that, determine how to proceed. I hope it is nothing too serious.
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