Sure, their "denning instinct" is kicking in. Don't want to soil the nest where they sleep, so they're doing their best to crawl out of it to toilet. They'll get better at it over the next couple weeks. Hope they are not on carpet!
OH GOD no try "UN-learning" them about NOT peeing on the carpet, Newspaper in the "play/feeding/toilet area" blanket or rugs in the "bedroom"