It happens, it sounds crappy but ultimately there's probably nothing you can do now. I'd imagine all your deadlines are now right before/during exams so trying to get them pushed back will only ruin your revision. It's also pretty normal to get essays you feel like you're guessing! I would just do yourself a plan, do the best you can do in a reasonable time frame, prioritise essays which are worth more... then move on. It's one semester, you won't go from 70% marks to failing, you can fix whatever damage is done further on. The university will also be looking at the lecturers marks and if suddenly everyone on the course does badly they will take action over it, it probably won't help you but rest assured it will be noticed.