1989 O-Pee-Chee New Kids on the Block Non-Sport Forum

Ok, I know this is likely way down the list on most peoples want lists, but I've noticed there is a light back and dark back variation within the set. I'm trying to figure this out.

Is there any difference between the sets other than the wax box was overlayed with a O-Pee-Chee "safety seal plastic wrap"

Also I've noticed what might be a 4th variant on some cards.

Anyone with any idea?