Trentsands gave good recommendations. He also said:
3) You can do an about-face and recalibrate your syllabus to provide additional in-class instruction on the assignment and postpone the due date. This seems drastic, but sometimes, especially early in one's teaching career, a person overestimates students' base skills and knowledge and doesn't provide students with adequate preparation for an assignment. Accepting fault and making adjustments is okay and the need to do this will decrease over time.
I've been teaching for twenty years, and I still do this if I need to.