Hello,

In looking at the pictures you posted, a few problems come to mind. First, the browning needles could be a result of transplant shock. Much of the outer growth on the arborvitae looks green indicating that the rest of the plant is healthy.

I can rule out seasonal needle drop- a normal occurrence for all evergreens. The innermost needles gradually turn yellow or brown and drop to the ground. Environmental stresses, such as drought, can cause greater than normal loss of needles. The needles on the outer growth remain green on healthy evergreens. Please check on the branches of the trees to make sure there are no insects causing the damage. If there are, your landscaper should be notified since your trees should be guaranteed for one year.

Perhaps it doesn't need to be stated, but it is important: it never matters how often you water. What does matter is how much you water. The water needs to reach and surround the plant's root zone. Do a test. How long does the soaker hose need to run for water to permeate the entire root zone? Does the soaker hose circle the plants? If not, part of the root zone may never get enough water.
Water is key to helping the plant acclimate to its new home. Feel around the root zone of the plant and make sure that the entire zone is saturated. If not, then you need to move around the soaker hose to make sure the entire zone is watered.

These trees normally move around in the wind, but they should not be tipped in their planting holes. As for feeling hollow underneath, I’m not exactly sure what you mean but I believe that it is worthwhile to call your landscaper and inquire about the tipping and the tilting. It sounds as if they might have been planted improperly.

This website has an excellent handout on arborvitae.

https://extension.oregonstate.edu/ask-expert/featured/arborvitae-root-issues-should-we-dig-it

Let’s hope for simple transplant shock, though the tilting is still a problem.

I hope this was helpful.