It's difficult to tell from your photo exactly where the tree is browning. I do see the dieback of the top of the center tree. Are the tips of the needles turning brown all over the tree? Just on one side? On one or all of the trees? Your question is one that we are see frequently. Blue spruce is not suited to our area. With the unseasonable drought, heat, wet, and cold that we have experienced over the past several years, it has come to be very evident with their demise.

Spruce trees can exhibit a number of problems caused by weather, environmental problems, insects, and diseases. There are many noninfectious problems that can mimic diseases. A few possibilities include an imbalance in soil pH, poor fertility, fertilizer or chemical burn, root injury, root rot, and drought stress. Some diseases on the blue spruce include the Cytospora canker and Rhizosphaera needle cast. It could also be mite damage. The mites are spider-like creatures that suck the sap from spruce needles, so that when viewed under magnification, the needles appear speckled with yellow flecks. You can scout for mites by shaking a symptomatic branch over a white sheet of paper and then looking for tiny, moving dots (mites).  

Your tree may have a fungal disease, or an insect is also a possibility. However, it is important to correctly identify the issue causing the branch die-back before proceeding with any solution. I am going to suggest that you submit a sample to the MSU diagnostics lab for identification. Include branches affected with the die-back along with areas that don't seem to be dead. The better the sample, the easier it will be to identify the problem. Be sure to include healthy needles as well as needles that do not look healthy. Here is the link for information on how to submit a sample, the forms that are required, and the cost:  http://www.pestid.msu.edu/SampleSubmission/tabid/58/Default.aspx

The alternative would be to find a certified arborist in your area. This link gives information on why you should use a certified arborist and how to find a local arborist: Arborist Directory. If there is a phone book for your area, you can look under arborist. Be sure that the information contains the logo for ISA Certified Arborist.

Below are several links explaining Cytospora canker and Rhizosphaera needle cast which are two common diseases of blue spruce. All include photos of the disease. These may also help to better identify the problem:

• Rhizosphaera Needlecast on Spruce
• Cytospora Canker of Spruce
• Common Diseases of Blue Spruce
• Cytospora Canker
• What’s Going on with Blue Spruce?