Speak to your students, especially if they are struggling with their grades. This is a tell-tale sign that something is wrong, and even if it’s not due to a personal problem (depression, anxiety, family problems), you are one step closer to getting to the root of the problem. It’s never a bad thing to be reassured, especially when it comes to the overall well being of a student.
Provide support, even if you can’t be the one to do it. Refer the student to a counselor, and be a person that the student knows they can get help from when they need it.