I planted about 20, 4' tall arborvitae, almost a month ago. All but one were completely green with no sign of brownage. Within the last week or so, nearly all of them have been turning brown, mainly on the interior of the plants. I was told by the greenhouse to only water them once a week, which is what i've been sticking to (except when it rained) any ideas?
i attached a few pictures to help.