That's really odd. Unfortunately I can't help you much because I don't have a guitar with a TOM bridge. I use GHS Boomers. On my Jackson with a Floyd I use Spud's technique of running the ball end through the tuning peg so even if my strings were doing this, I'd never see it. I've found D'Addarios to be darker than GHS. Some folks like that, some don't. I prefer the extra brightness.

I wonder if the place where you got the loose strings from just got a bad batch or something. I've never heard of that happening before.