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.
I hate to tell you this, but that species won't last long term in your neck of the woods. There was a guy in KY who decided to start growing redwood because it is illegal to harvest from the California stands. The trees made it a few years, maybe even over a decade. The first massive wind storm that went through once they were adolescent trees ripped them all up by the roots, because redwood/sequoia roots go wide, not deep. That also may be one of the issues having it in a pot. It may be root bound.