Hello,
Given the timing, I would suspect spider mites are the culprit. These tiny mites suck the juices from the needles, causing a browning. You will need to look closely at the branches for the mites as well as possibly some webbing. It may be that the population you have can be treated with a strong spray of water two or three times a week for a few weeks. This method has the advantage of not harming any beneficial insects who are there to help you out by feeding on the mites. These can also be treated with a miticide that you get at your local garden center- just be sure to follow the directions and purchase a product that lists dwarf Alberta spruce as appropriate for treating. The problem with this method is that sometimes you can get a surge of mites because you have removed all of the mite-predators. Please read the following article to get more information and treatment recommendations: https://yardandgarden.extension.iastate.edu/article/2016/06-10/mites.html
New growth will eventually fill in, but it may take some time.
Thank you for contacting Ask Extension.
Ruth