Arbor Vitae leaves turning brown
We had a row of Arbor Vitae around 25 ft tall and 2 leaves turned brown and then the tree died .. now the next tree leaves are turning brown ..afraid I’m going to lose the whole row It is wet in that area but never bothered them before they have been there 7 years
New Castle County Delaware
From your photos, it appears that the green growth on your tree was healthy. Arborvitae are prone to scale and/or spider mite damage. So if there are no signs of insects on your trees, the problem is likely root rot. We have had a very wet spring, and if the area where your trees are does not drain well, the roots will not be able to get enough air. (Yes, plants need oxygen for their metabolism just as we do. Roots cannot get it from photosynthesis so they get it from air in the soil. Soggy soil won't provide enough oxygen.)
Besides hoping for more gentle weather in the future, one small thing you can do with such large plants is to add a layer of mulch. Don't make it more than 2-3 inches thick, and don't put any near the tree trunks. This will help but is certainly not a cure. If your property allows it and since water obeys the laws of gravity, you might be able to dig some areas away so that water drains to a lower area. If you can do this, be careful not to dig close to the trees as most of the growing roots are here.