Anyone have any idea what is causing this? I’ve looked it up and found that at least for younger saplings. Some Browning can be normal in early spring, but none of the images had nearly this much Brown. There is barely any green left among the needles.
That’s what really indicates it was winter kill.
Winter kill is often caused by damage to the water transporting section of the plant (xylem). Think of it as a straw that connects the roots to the leaves. If you make hole in the straw, crush it, etc the water stops flowing. This is what likely happened here.
The majority of the water transporting parts of the stem were damaged. When the weather warmed up, and the plant came out of dormancy, the plant needed lots more water. It’s damaged system couldn’t keep up with the demand and tissues died.
Winter kill is most common because of rapid temperature changes. So a mild winter followed by a sudden polar blast that drops the temps by 50F or more will do it.