First litter in the new colonies? Mice will eat their first litters. I think that even if they have had litters before, they might still eat them after everything has been changed. How is the protein in you feed? and i'm assuming they have feed and water all the time? I'd give them at least 2 more litters. Then, raise up any survivors for new colonies. I've honestly never heard the tub size thing. Unless your tubs were really small, i don't think that was the cause. What ratio are you using in the colonies?