Aaron must be a knave, because a knight would never make the false statement that all of them are knaves.
If Bohan is a knight, then Bohan would be speaking the truth if Crystal is a knight, so that is one possibility.
On the other hand, Bohan might be a knave, in which case his statement is already false, regardless of Crystal’s identity. In this case, if Crystal were also a knave, then Aaron would have told the truth, which is impossible.
So, there are two possibilities for the ordered triple:
Aaron: knave
Bohan: knight
Crystal: knight
And,
Aaron: knave
Bohan: knave
Crystal: knight
Therefore, the Aaron is a knave and Crystal is a knight, and it cannot be determined what Bohan is.