Watering is advisable if conditions are dry. However, we don't have enough information to evaluate the prospects for recovery. It's important to identify what's causing the decline. An on-site inspection by a forester or certified arborist may be needed to do that.

In the meantime, see if you can identify the problem by using this diagnostic tool:

Spruce Problem Diagnosis for Yard Trees
http://files.dnr.state.mn.us/assistance/backyard/treecare/forest_health/whitesprucediagnosis.pdf