Could be pine weevil infestation.

Colorado blue spruce is susceptible to cankers and white pine weevils. The weevils cause the leaders to die back. Cut off dying leaders before the damage reaches the first ring of branches and choose another branch to train as a leader. Stake the new leader into an upright position.

Read more at Gardening Know How: Colorado Blue Spruce Planting Guide: Tips On Caring For Colorado Spruce https://www.gardeningknowhow.com/ornamental/trees/colorado-blue-spruce/care-for-colorado-spruce.htm

Since the tree is 30 years old, I don't think the problem is environmental. So I'm inclined to believe it's an infestation.

I wouldn't rule out the dry summer as it could have made the tree stressed and this is the way it is coping. After all it will be quite a large specimen and it is the worst drought since 1976. But certainly look for pests.

I would suspect some kind of bark beetle damage, particularly after a dry summer.

Sap oozing from cuts is normal for pines and their kin. It's how they protect themselves from boring insects. Sap flow is reduced in drought, which may allow an infestation to start. Usually, the first sign of a bark beetle infestation is dying branches.
Also, pines in temperate climates usually live upwards of 200 years, so I doubt that old age is a factor.

you could send an email to the RHS advisory service with photos and of the sap oozing branches and see what they come up with. if you are a member advice is free not sure what it costs if you are not but worth a try.

Sheer luck if you see the beetles. The larvae are the ones that do the damage, and they are hidden under the bark.

I read these trees can live for over 800 years