Just an update: it was clearly a stomach bug. The weird poos, lack of appetite, and slight listlessness hung around for about a week. Now she is bouncing off the walls and eating like a teenage boy :-)
How do I know it was a bug, you ask? Because I wound up with the same exact thing :-(. DH is busy washing the house down with bleach!
We did get some probiotics, and I can't say for sure as we were already on the upswing, but I do think they made a difference! Thanks fir the suggestion!