Depending upon when you began to notice the problem, this could have several different causes.

It could be a Tip Blight which, as you note, is a fungal disease. One of the clues for this are the raised black lines along the midrib of the infected needles.

Another thought is that it could be Rhizosphaera needle cast, also a fungal disease where the tree is infected each spring and, therefore, is considered chronic, where infected needles turn brown or purplish brown late in winter or early spring; however, from your photographs, this may not be likely as needles at the branch tips remain green with this needle cast, while older needles closer to the trunk of the tree become discolored. That does not seem to match your photographs.

It is also possible that this was caused by Winter Injury to the tree, where needles turn brown or purplish brown in late winter early spring. See this link for more information about this and other issues: https://apps.extension.umn.edu/garden/diagnose/plant/evergreen/spruce/needlesdiscolored.html

Unfortunately, if this is caused by a fungus, there is no treatment that “kills” the fungus and keeps it from coming back. However, there are sprays that keep the infection to a tolerable amount each year. After a few years of successful treatments, you may be able to stop treatment for a year or two before resuming treatment again.

To determine if your spruce trees are worth treating, consider how important the trees are to the landscape.

Here is an additional link that you may find helpful:
https://www.canr.msu.edu/news/what_is_spruce_decline_and_what_should_you_do_about_it

If the trees are important to the landscape and to determine and assess the extent or level of the infection, you may find it helpful to consult a Certified Arborist for an on-site inspection. We suggest Certified Arborists because they must pass a test and must acquire continuing education. You can locate such individuals at http://www.treesaregood.org/findanarborist/findanarborist.aspx