Hello Mark: It would be normal for Arborvitae to lose interior needles this time of year. Each year needles are produced on the outside and needles will be lost on the inside. Green needles have minerals and nutrients moved out leaving a yellow color which later turns brown and either hang in the tree or fall to the ground. They may need to be watered now as we have had another dry spell. Do plan on watering them one last time just before you put the hose up for the winter to ensure moisture in the needles. Watering should continue until you see normal amounts of growth. This is thpically by the third growing season.
