Gradebook

I have a very odd issue with my gradebook. While the totals are correct and include all activities, if I look at an individual student record showing their grades on various activities, two quizzes simply are not listed at all. They show up on the student's activity page in their profile, but not in the gradebook. I looked in the database and don't see anything in particular about those two quizzes that is different from any other so I don't know what to make of this.