It sounds like it's likely from the antibiotics to me. Also, raisins have a pretty good "laxative" effect so combined with the antibiotics it might have given her diarrhea. I think with antibiotics the runs can come and go throughout and after the course.
From the people I know that have a sensitivity to sulphites, it usually results in a headaches and/or hives. But these are adults not kids so I'm not sure how it manifests. Have you ever given her anything with other dried fruits in them? Like apricots, cherries, cranberries? They almost always have sulphites....so if she didn't have a reaction to that then she likely doesn't have a sensitivity.
Has she had eggs yet? (Here in canada, it's reco'd that LO's don't have egg whites until 1 year, not sure where you are?). If she has never had egg whites, most cookies have eggs in them. It could be that.
Not sure if this is your first LO in daycare or not but I found with my first daughter that the first year in daycare was brutal. It seemed like every week she had a new cold, the runs, a rash or a fever. It was horrible!! But they get over it and end up with a healthy immune system!!
Good luck,
lilysmommie