Since my focus was mainly on group B, apart from his actions on group B, I didn't notice anything and I don't know how to check if he is really ok or not. If I ask him he says yes, and when he says no, he blames his ex and group B.
I don't want to criticize his work on group B, I'm very uncomfortable talking about people that are not present.
I'll think how to do it, but it is hard since there is no "red flag" but a lot of tiny ones.