Amy

It looks like your arborvitae are experiencing an environmental problem rather than a pest or disease issue, but please check the bushes to make sure you do not see any pests, including bagworms. Bagworm (psu.edu)

Some branch dieback is common on arborvitae. Extreme changes in soil moisture, abrasion from ice, snow or plant wraps, shearing, overly dense branch structure, root damage from too much moisture, or too much salt (from roads, driveways or fertilizers) can also cause issues.
This summer, the incredible heat and either drought or downpours, in some areas, have caused a great deal of stress for trees.

Here are some things you can do to help your plants grow more roots and eventually more top growth:
– Hold off on fertilizer; let the roots recover before stressing the plant into foliar growth.
– Water deeply during dry spells but allow the soil to become almost dry between watering to prevent root rot.
– From the outside, remove any dead branches or branchlets, making a clean cut with bypass pruners.
– Now look inside the plant. If the interior is very crowded it can prohibit air circulation inside the plant. Remove any dead, crossing or broken branches, branchlets or needles, stepping back as you work to keep the plant symmetrical.

Hopefully, with some TLC your shrubs will recover but it may take a season or two.
All the best,
Roxanne