Spruce tree issue
Good afternoon, and thank you for using the Ask an Expert service.
It is difficult to determine the cause of the needle discoloration based on pictures alone. Several factors can result in needle discoloration and drop, including some of the factors that you mentioned.
In order to properly identify the cause of the needle drop and the discoloration, we would need to take a look at the needles under a microscope. Here is an overview of common spruce diseases and pests: https://files.dnr.state.mn.us/assistance/backyard/treecare/forest_health/whitesprucediagnosis.pdf
I would recommend that you bring a sample of one of the affected branches (please bring a sample of a branch with both live /green needles in addition to discolored needles. This 'transition area' is the optimal place in which to find the presence of spores, and other causal agents.
Our extension office in Garfield County is located at:
1001 Railroad Ave.
Rifle, CO 81650