I have a pen/ den set up for my puppy (17 weeks old). Also there while I go to work. She's fairly recently did a couple of times poos in her bed but it was only those two times since being in this particular set up. Now she did it again and I think her poos are a bit loser but some are ok. She has been transitioning to a new food over a week...i mix it in with her original food... So after some weeks why is she starting to poo in her bed?