I've suggested them to chat with their doctor.

Many (including myself) have been successfully living with symptoms without treatment, but seeked my eoctors advice after having similar symptoms after a similar situation, and the result was adhd medication which helped.

Suggesting that someone talks to their doctor about symptoms is reasonable advice.

Edit0: and I wouldn't go around diagnosing people with depressive episodes from a single comment, were I in your shoes. Let their practicians do diagnoses, you know?