I have a question regarding neutrals in a residential panel that are extremely discolored as well as the neutral bus jumper.

I am wording this as a code question pertaining to anti oxident...as I am wondering what thoughts you guys have on this. The electrical sub-panel (main is on the 200 amp meter) in question is a fairly new Cutler Hammer CH, with arc fault breakers and is located in Texas.

Would failure to use antioxident on aluminum wires per NEC have anything to do with the discoloring?
Perhaps loose neutral in panel, however that would that probably just throw 240 volts across circuits and wipe out a bunch of stuff?

My brother-in-law was told by electrician that it could be from a lightning strike...no surge protection, this is the second time a breaker was replaced due to tripping by the same electrician who pointed out the discoloring on neutral bus jumper on his first trip.

Lastly, I think a megger test on all his home runs would be prudent...what say you?

Thanks in advance.