It looks to me like several of those branches have broken, perhaps from heavy snow or ice accompanied by wind. If broken, prune off below the break. My arborvitae/Thuja have filled in well when I pruned out limbs broken in winter.

arbs are trees.. and they are conifers ... and imo.. treated as such ...

i would doubt it will ever have any need for fert .. ever ....

what babs said about winter..

but since it was transplanted just last year ..... it could also be wholesaler.. retailer damage in shipping from the grower ... moving to your house.. or planting damage ...

but it was minor enough that it really didnt show.. until the drying winds of winter desiccated the minor damage .. its hard to tell when something happens to an evergreen ... because they can stay green a long time ...

you are responsible for water this year.. and especially if there is some drought in summer ... and then after that.. it should be free range ... with only the snow/ice issue in the future ...

frankly.. it doesnt look that bad.. and once you remove the brown.. you and it will forget about it ...

ken

read up on proper watering

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub