People often reveal more after feeling understood than after being questioned aggressively.

Pressure closes people down. Interrogation, however well intentioned, puts someone in a position of defending, and defending is not a state in which anyone volunteers anything. Feeling understood does the opposite: it removes the need to protect, and what was being held back tends to come out on its own.

If you want to know what is going on with someone, lead with understanding rather than questions. Say what you have noticed and that you are not looking for an explanation. Then leave room. What arrives that way is usually more honest than anything you could have extracted.