I have a bottle baby that is getting Advance brand kid milk replacer. she is acting fine (hungry, playing, active) except she seems like she is struggling to poop. she will squat down like a dog but doesn't produce much at a time and what she does produce is yellow and slimy looking. this has been going on for about a week and her belly isn't swelling up like she's constipated and no changes in behavior. She is in a pen with all the other babies and moms, so she could be pooping other time when I don't see it. I do seem to see it mostly after I give her a bottle, but occasionally other times. Any ideas?