This is going to be vague and I apologise in advance if that is frustrating but I won't be drawn on specifics, I'm afraid.
I have professional experience of working with children and young people with certain SEN. A very close friend's child is starting to present with some signs that they might also have one of these needs. The child is in Infants and slightly younger than the children that I encounter professionally, and would probably not receive any formal diagnosis (if indeed this were necessary) for a couple of years yet, but it is a need which tends to respond well to early strategies. The child is starting to misbehave at school and I think the two things might be related.
The question is whether I say anything to the parent, who is one of my closest friends. I would be particularly grateful to hear from anyone who has been in the parent's position in this situation.
YABU - keep your beak out, hope that the professionals who work with the child are noticing the same as you and be supportive if and when any assessments start.
YANBU - gently say something.