I planted this group of arborvitae along a north fence of my property 7-8 years ago. They have grown to twice their original size but seem to be dying off at the bottoms. They remain fairly lush at the tops. What do you think is going on with them? Should I trim those dead branches?
My guess would be rabbit damage. Arborvitae is especially attractive to rabbits. Unfortunately, in the areas where there is nothing green, the plant won't come back.
My suggestion would be to wait to see if you get some regrowth. Otherwise, you have three choices: remove and replace the plants (and protect from rabbits); plant something low (hosta?) around the arborvitae to cover up the dead areas; or live with them the way they are.
Physical barriers are the best way to protect from rabbits. A fence has to be two feet higher than the anticipated snow line. Read here: