NO.
No one should write anything. It’s a C, not a D, not an F. Do you really want to explain mental health issues, when AO’s view them as possible red flags? It doesn’t matter what caused your mental health issue. Barring stays in psychiatric facilities, hospitals, extensive time out of school, and so forth, no, don’t mention it. And if one of those situations applies, your GC is primarily the one who should address it. A C doesn’t constitute urgency.