Think of a class of students learning a foreign language. You set them a communication task and they work in pairs. making use of whatever linguistic resources they have to achieve a resolution of the task. You, as the teacher, then move round, listening to what they are saying, or trying to say. You realise that someone needs help, even though they may be in full flow.
But what do you do?
The received wisdom is that you should intervene without interfering, ie, offer support but don't kill the flow by being prescriptive. Now, if anyone can tell me how you can intervene without interfering, I would like to hear from you. You see, if you do nothing, your students will think you don't care, or that you are not earning your pay. But if you do intervene, however skilfully, they can think you are interfering.
All I will add is that being a parent is in some ways like being a language teacher. I guess the answer (if there is an answer) is to sit back and wait till your students ask for your help. And if they don't, it's either because they don't need it, or because they no longer have faith that you are the person to help them.