In Act 2 of Macbeth, who suspects Macbeth of being guilty?

In Act 2, the only suspicion of Macbeth that arises comes
from Macduff.  In Scene 4, the very end of Act 2, Rosse, Macduff, and the Old Man
discuss the murder of Duncan and the flight of Malcolm and Donalbain.  They discuss the
fact that the other noblemen suspect the king's sons of foul play because they have fled
Scotland and now look guilty; however, Macduff does not agree.  When asked whether he
will go to Scone to see Macbeth's coronation, Macduff replies that he will not go and
will instead return to his home in Fife.  This is an outright act of defiance on the
part of Macduff who as a nobleman would likely be expected to attend the ceremony.  So,
Macduff's actions suggest that he does not trust Macbeth.