Was the liquid clear or anything? It might have been urine with it. Or was it basically diarrhea? A soft/runny bowel movement might mean parasites or something else like that. Not 100% sure though. I'm no vet.
I remember a month or so ago, Pelota left me a present and it wasn't her usual solid log, but it was a bit soft. Ever since then, though, her bowel movements have been fine. If you can though, it probably wouldn't hurt to bring it to a vet for a fecal exam.

Don't you love poop topics? Especially when you're trying to eat your oatmeal. Mmmm.