Those wheels are pretty cheap so it is probably metal fatigue. Considering they haven't probably ever been serviced and they are not made of quality parts and the bike is of unknown usage before you got it but probably at least 30 years. Those wheels probably aren't quite that old but considering they are newer could mean that their was issues from the previous owner and maybe they were heavier or carrying a lot of extra weight or didn't maintain their bike or whatever.

I would probably just get some new wheels and maintain them with some regularity

Not sure why paint it to be a different brand unless it was a sponsorship thing. Specialized is a good brand and their old paint jobs were neat.