You saw Fatgum running around, when you asked him what was wrong he talked pretty fast, but you could understand, "The boys are sick so I have to go get medicine and other things." He had said a few days ago Tamaki, Kirishma and Tetsutetsu were all showing signs of sickness, so they probably all got colds, but Fatgum being the adorable overprotective dad he was, was acting like it was the plague.