HELP!! My daughter's past two diapers have had VERY liquidy poops! The pediatrician on call sounded…

HELP!! My daughter's past two diapers have had VERY liquidy poops! The pediatrician on call sounded out of it, and said there's no need to take her into ER. But she might have a stomach virus or change of diet could have caused it. Neither of us have had a change in diet! She's breastfed, and has been on the same supplement since birth.