Answer: Usually tip browning would be caused by sun exposure, lack of soil moisture and possibly even old frost damage. In this case I would suspect it is due to too much sun possibly also combined with soil on the dry side. In damper soil they can handle more sun than they can in dry soil. The soil should be evenly moist like a wrung out sponge, and a layer of natural mulch several inches deep can also be helpful. New plants are still becoming rooted and so will be more susceptible to moisture stress than well established plants would be. There is also the possibility of some frost damage that occurred last spring and went unnoticed until now. When the plants become heat and moisture stressed it taxes the circulatory system and this can then reveal that damage months after it really happened. Overfertilizing can cause fertilizer burn and damage the roots and inhibit taking up moisture, foliage damage can also occur through accidental contact with herbicide. There are many possible reasons. You could trim the brown areas off, but they will not grow back this year. I hope this helps you troubleshoot.
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