Baby poop smells like...fish?

My daughter had a blow out diaper at school, one at home also loose, then just had another. The most recent was very pale almost white and smelled like rotten fish (only thing I could compare it to is smelling exactly like a dog who had their anal glands expressed if you have ever smelled that). Could it be a virus or reaction to food? She is 18mo and on a typical toddler's diet. Anything you guys do to help with diarrhea? We are not doing milk tonight before bed and going to give her a culturel probiotic. Any other ideas?