Why is there moisture under some new wall plates in the basement?
Pressure-treated lumber is as juicy as a ripe peach. On many occasions I've been splattered in the face while cutting and nailing boards fresh out of a strapped unit. It weights as much as three times a dry board. I'd guess that the concrete is drawing the moisture out of the wood. It's not coming through the nail holes.
Run a fan to circulate things for a few days, and run a dehumidifier if necessary. See what's what then.