Dying? Short of water?
please post pictures

I ask the person in garden center how to take care of them. He said don't do anything. Just plant.

If they're turning brown, they're dead. Most likely causes are root damage when they were dug at the nursery, or lack of watering.

PS Leyland ;-)

Resin

As an aside, I don't know if the answer "Don't do anything" is ever correct when planting a new tree at the end of May. If you got them at a garden center, though, perhaps they have some sort of "money back guarantee."

Lowes does have a guarantee.