The first this to do is go out and check that dirt or mulch has not been piled up againts to trunk of the arbs. Brush away any soil or mulch until the original soil is visible. The crown of the plant (where the trunk meets the root flare) must be flush with the surface of the surrounding soil. Mulch or dirt piled against the bark impedes the flow of moisture and nutrients from the roots to the stems and foliage above slowly strangling the plant.
If you want to locate a certified arborist, here’s a link: https://nysarborists.com/for-everyone/find-an-arborist?view=Profiles&layout=search&task=civicrm/profile&gid=10&reset=1