I have run three tests on my panel and have checked the wiring during and after each test. I have not noticed any apparent problems until after the third test. When I checked the wiring after the test was over I noticed a black line on some of the neutral and ground wires (these did not show up during the test as I had the panel open and did not see them). I have not noticed any problems with how the panel functioned during test three and none of the breakers (either inside the control panel enclosure or the house panel) tripped. There was no "smell" or any visual indication of the wiring overheating (no apparent damage to the insulation on the wires). None of the terminals show any sign of overheating or shorting out and the hot side does not appear to show these black lines (at least on the red wires, black is kind of hard to tell). I "was" pretty confident that I had wired the panel correctly but now I am not so sure. I have attached a picture of one of the neutral wires. Any one have an idea what may be causing this? I do not plan on powering up the panel again until this is figured out. This looks like the wiring is overheating somehow, or am I just being paranoid?
One more thing, it seems like these black lines are running along the text that is printed on the wire.