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Hi, I have several emerald green arborvitae trees in my yard. I have two other emerald green arborvitae trees that are turning brown, but I am not sure what the reason is. I will upload images of them. Please let me know what the reason could be.

Certified GKH Gardening Expert
These trees can be sensitive to overwatering, and are very sensitive to soil infections. Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/ornamental/trees/arborvitae