Simon has been having frequent and bloody poops for that last couple of days, so I took him to the doctor this morning. She took stool samples to test for Salmonella and C. diff. but also said it could be a milk protein allergy. So no dairy products for me while we try to figure out what is causing the problem. So in a weird way, Salmonella is the ideal cause here, because it will run its course and he'll be fine. No dairy for ten more months will not be so fine.
The good news is that he is happy and acting completely normal, so I figure whatever is causing the problem can't be too terrible. It's just wait and see for right now.