Where have the needles turned brown? if the tips are brown then those plants have died, but if the needles behind the tips are what is brown that is normal as new growth replaces the old growth.

Evergreen could mean evergreen leaves too, not just needled plants...

When you planted these, did you loosen the rootballs well before installing in the ground? If the rootball was still in the tight shape from being grown in a pot, its entirely possible to water the surrounding area with none of the water going in to that rootball - the plant dries up and dies.

That's a guess without a photo of your plants, but a common early gardening mistake...

Can you provide a photo so we know what you're trying to describe?