Find out what actually happened
Look at the individual grades rather than the average. Nearly always it is one or two classes, and the average is just how you noticed.
Then ask which kind of problem it is. Falling behind on content — where each week builds on the last and a gap compounds — is different from missing work, which is different from a term where something outside school made everything harder. The three have different fixes and treating them the same is why "try harder" usually fails.