In my limited experience it's usually a result of stressed females. I worked at a pet store and had to manage about 40 breeding groups of mice, rats, and hamsters and it seemed first time females had a higher than average chance at eating babies (maybe stressed from being a new mom) and when we did very complete cleanings (cages, shelves, floors etc) sometimes there would be several mothers kill/eat some or all babies. I've heard but never tested or seen for myself that a lack of quality food can be the cause as well. Regardless of why, any adults that killed babies more than a couple times became food.

you mentioned a back porch and laundry room? what are temps like and are they high traffic areas where the mice could be stressed?

I'd keep trying... keep the adults in a calm low traffic place with comfortable temps. if the females eat another batch of babies, get some different adults.