I live in northeast Georgia, USA, and I have a large fir tree growing in my backyard. Over the past month or so, I've noticed some of the needles along the branches are turning yellow. I have no idea why, or if this is normal for this kind of tree. We bought this house about 2 years ago, and in that time I haven't seen it turn this shade of yellow before. It definitely didn't last October. Should I be concerned about this? Thanks in advance for the help.
Here are a few pictures of what it looks like: