One good indicator of over training with your arms is the measurement of them. F the arm is the same size, you are good to go. If the arm is larger, then great. That means that the muscles are overstressed big time and are receding. I hope that this helps you all.
Injuries play a very important role.
If you are injured then you can't train thus, no big arms. I will cover some arm injuries and some ways to correct this. Keep track of what you do in the gym. If you try a new exercise and the day after you hurt in the wrists or elbow, then don't keep doing that exercise. I do it all the time.