Blue Spruce yellow needles...need advice

I have a 10-yr blue spruce west facing, full sun,about 25 ft tall....the needles on the inside lower branches are turning yellow. Also have noticed that the mulch at the base of the tree seems to have some mildew, not that this would be the issue...but I don't know. Any thoughts on why the needles are turning yellow and what I should do to make sure it doesn't die. Any thoughts, ideas and suggestions are greatly appreciated.

Thank you,
Ron
ron.gillette1@gmail.com