Austrian Pines have a natural needle drop of (innermost) needles that are 3+ years old.

In our dry, windy, hot-summer, low-humidity climate, needle browning on pines is expected and normal. Water the rooting areas of these pines in dry winters when it's been warm and there has been no snow cover. It can help to use the needles as mulch to maintain some moisture but do not let them get more than about 6 inches in depth. Additionally, the recent flash freeze caused much damage to needles and this may also be relevant since the damage you noticed is very recent.

Most needle blights or needle casts do not occur in Colorado but will be seen in our neighboring states. You can have it properly diagnosed by a certified arborist first, then control includes 2-3 fungicides sprays, beginning in the spring, using a labeled fungicide containing copper or chlorothalonil. The applications are also best made by a certified arborist.

See (3) photos of normal needle drop from Austrian pine below.

Here is a good article on brown pine needles:

https://extension.colostate.edu/topic-areas/yard-garden/winter-drying-is-a-likely-cause-of-brown-pin...

To contact a certified arborist, see this link:

https://www.treesaregood.org/findanarborist