Dying evergreen trees
Hi -- Dieback like this can occur because of problems in the root system and/or failure to establish after planting. Bagworms also can be a problem in these plants, so check to see if any visible "bags" are present. Here is more information about bagworms and what to look for, https://extension.umd.edu/hgic/topics/bagworms-trees-and-shrubs.
You mentioned that these were planted last year. If they had too much or too little water after planting, that could have led to root decline, resulting in failure to grow. Last year and into this spring we had excessively wet weather in our region which led to root problems in many plants.
Also, sometimes plants die a year or two later if they were not correctly planted initially. For example, if these were root-bound in their original containers and the roots were not teased apart at planting time, the roots may not have gotten established into the native soil. Woody plants also need regular supplemental watering for their first 12-18 months after planting if there is not enough rain, to help their roots get established.
Unfortunately, the brown plants will not recover and will need to be replaced. Take care to consider the drainage of your site and planting technique. On our website, you can find further information about planting trees and shrubs and how to care for them after planting. https://extension.umd.edu/hgic/topics/tree-shrub-planting