LysmachiaMoon said:This looks like weather related damage/stress to me. The key is these are very newly planted arborvitae and they are still establishing their roots. Very new growth at the tips can be browned by too much sun, too much wind, early frost, etc. As long as you are seeing new fresh growth on the trees and no moldy areas or the dreaded bag worms, I would think time is all that's needed. I've got two massive hedges of arborvitae; they can look a little scrappy until they get really well established. To get the middle portion to fill in, you could try pruning back the top. It will stimulate outward pointing growth that will bulk up the plants.