Deb

Well from the photos, I can't see too many yellow leaves. It might be that if it was previously growing outside, in a very warm, but dry environment, perhaps the humidity in the bag was too extreme a change for it and it set up a chain of events inside those leaves that is resulting in the yellowing leaves. From what I see it does look pretty healthy and it might be that it will need to shed some leaves before it gets back on its feet. But I have found that chinese elm are pretty hardy and I'll bet that it will bounce back.

Will you keep it inside or do you plan on keeping it outside through the winter. I have done it both ways although the windowsill that the inside ones were on was very bright and cool as I turned off the heat register that was under the window. Good luck with your new tree.