It's not dying.....it's dead. And a few of its neighbors in the bottom photo are not looking too great either.

Did you plant them or were they done professionally? How deeply? Amended soil? What did the rootballs look like? What's the watering regime like (device, frequency, duration)?

I can say that they are planted way too close to that fence. And probably too close to each other as well.

"the irrigation is pretty even along this bed."

If you've been relying solely on an irrigation system to do your first-year deep watering for you then I'm guessing that's a huge part of your problem.

This happens. Unfortunately, whenever you plant the same item repeatedly, one dead/diseased plant leaves a glaring hole. Much better to plant a variety. Most of my property is lined with some large fast growing evergreen, and those dead spots happen. They are about 20 years old now. We’ve had to take down a couple, and luckily they have been at the end. They do give us wonderful privacy, shade and wind block. We did not plant them.