Answer: It is possible that what you are seeing now is normal because spruces will drop some of their oldest needles each fall.
On the other hand, since these are newly planted trees and there have been some stress problems, I would suggest you consult with your county extension to make sure there is nothing else going on because there are various insects and diseases that can cause needle drop.
In terms of watering, your goal is to keep the soil evenly moist but not sopping wet. Using several inches of organic mulch over the root zone (but not touching the trunk) and applying water as a slow deep soaking will help maintain that soil moisture down deep where the roots are. (A daily light sprinkling usually will not.)
The only way to tell how effective your watering is (or isn't) is to water, wait several hours, then dig down into the soil and see. To judge when to water again, check the soil with your finger. When the top inch or so has dried, water again. In the fall, as the weather cools and there is more natural rainfall we usually need to water less and less because the soil stays moister longer on its own. Keep checking though up until the soil freezes.
Good luck with your trees!
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