what is wrong with my evergreen?
This looks like a hemlock tree. We could not accurately identify what the problem may be. The decline of the branch may be due to excessive shade and possible insect issues such as the hemlock woolly adelgid https://extension.umd.edu/hgic/hemlock-woolly-adelgid-trees, scale https://extension.umd.edu/hgic/scale-insects-hemlock, and mites https://extension.umd.edu/hgic/spider-mites-trees-and-shrubs, etc.
Hemlocks can also suffer during heat. They have a very shallow root system and appreciate more moisture during dry periods. You will have to look for all of the above.
If you would like an onsite diagnosis regarding the health of the trees, please contact a certified arborist for the best way to proceed http://www.treesaregood.org/