Is it possible they are hearing something/someone outside at that time? A neighbor that leaves for work really early? Dog-walkers going by? Not sure how likely that is, but it must be something that's happening at the same time every morning to disturb or excite them. One of my female ducks, for example, gets REALLY excited and quacks really loudly when she hears my husband's voice, even if she is locked inside the Duck House for the night and can't see him. Just a thought.
 
Possibly moving the duck house will make a difference and break whatever is causing this cycle? It would be such a shame to have to get rid of them for this reason. :/