The arborvitae I planted a year ago are very brown right now. The inner branches are very green but the outer branches are brown/rust colored. Is this normal or should I be concerned?
Get under there an check that you didn’t bury the trunk too deeply into the soil. Where the trunk entered the soil of the ball or pot that you bought it in wants to still be visible after planting. Likewise you don’t want mulch piled up against the trunk either. Brush back any mulch or soil away from the stem until you find the original soil and keep it that way. Mulch or dirt piled against the stem prevents the easy flow of water and nutrients from the roots to the foliage above. It is a common mistake and the #1 reason we have to replace plants under our lifetime guarantee…stems buried too deep or mulch piled against the bark. More on that here: http://blog.timesunion.com/gardening/planting-101/6841/
Keep snipping off any brown foliage.
Feeding them would also be a good idea…Tree-tone would be the best. Get that into the soil right away to help it get some nutrients to start filling back in.