What is brown will not green up. Winter burn or a host of other issues especially if they are new plantings last year can be taken into account for this dead foliage. If it is just random parts of the plant it could be going through an adjustment process especially if they were b&b.

A little more information would be helpful rather then looking at a partial photo of this plant and trying to give you a meaningful diagnosis as to the issues confronting it.
Maybe a call to your local county extension agent should be your next step for a correct diagnosis. That my recommendation.

Look like Thuja occidentalis 'Smarged' aka Emerald Green foliage.

Dave