Why is my emerald cedar turning brown from the inside out?

It is very difficult to tell what the problem is without looking at the plants, but it is very likely a problem with the roots or soil. Often, when plants come from a nursery that mass produces plants, they damage the root system when preparing them to sell. If you lightly remove some of the soil from the roots, you can check for damage and make sure you have a lot of fine roots that are needed for the health of the tree. A soil test is also recommended to be sure your soils have the right nutrient levels for maximum health of your trees.