[theSage]

Hmm, perhaps I should have said "How to investigate if something went wrong?".

You're right that people leaving is normal. What I'd like to be sure of is that they are leaving because of the right reasons.

[neltnerb]

Just ask them about what they're doing next and what they're excited about. If they want to get into details it might give insight into what they've been missing, at least you'll get to know them better.