It appears that your 5D3 has the same issue that mine does... in the far bottom right corner of the image it has a more purple hue than it should. It is more noticeable in your NR 25 image. On my 5D3 it is most noticeable at ISO 12,800 and above, but sometimes at ISO 6,400.
Yes, I see it in both CR2 raw files I uploaded as well (taken moments apart), but it mostly is gone when LR opens it with default settings...but I hadn't noticed that before...
Anyone else seeing these at very high ISO/low lighting?
Yes, it's pretty common. I think Canon may be working on a firmware update to help with this.