It has been known for a long time that people with autism generally have intestinal problems as well, and that these are often coupled with abnormal microbiomes.
Clinical trials have indeed shown that probiotics (a mixture of bacteria found, for example, in yogurt) ease the symptoms of people with irritable-bowel syndrome, who often have slightly abnormal gut microbiomes.
This happens often when it rains heavily, but the principal sensed something abnormal was up as parents rushed in faster and in greater numbers than usual.