When the unit's status is less than great, as the producer you will have a word with your idols to try and improve things.
To tell who is getting the lecture, look for the girl who, during the lecture, (immediately before the choice) changes her facial expression or starts shifting around uncomfortably.
In case it isn't already obvious, this page is pretty much 100% spoilers!
If you succeed at evening communication, the idols' Intimacy Score will increase. However, if you also get a decrease during morning communication, even if you succeed at evening communication, the unit can remain in a bad status.
For example:
In general though, if you fail, the Intimacy Score will decrease, and if you succeed, it will increase.
If you fail at both morning and evening communication, it seems you can get to bad status in as few as 5 weeks.
In the case where, through morning communication, the Intimacy Score has changed greatly, even if you resolve this through a lecture, there are times when your unit can end up in a different bad status, e.g. "Showoff" → "In-Fighting".
The evening lecture in the end only slightly improves the current situation, so after returning to a normal status, it is still very important to maintain the girls' balance.