Well what happened was the copperband out of nowhere just started swimming extremely fast and erratic. It ended up crashing into rocks and landed where the tang sleeps. It was then and really only then going after it. It was only really getting it out of the way during feeding before, no real aggression.
Ended up taking the copperband out, but wife and I decided we didn't want to get rid the tang over such a delicate fish like a copperband that has a high chance of just dying overnight for no reason.
So we put the copperband back in the main display, and so far, everything is back to normal. Hopefully this was just a weird one day deal.
The powder blue we had was absolutely trying to kill a copperband we had before. This orange shoulder is night and day different from it. So it'll stay with us!