It does appear that there are only three chicks now. I just watched a feeding and there were only 3 faces, 2 larger chicks and 1 smaller. A few days ago there were four, and just to check, I went to another forum where pictures had been posted by two individuals that clearly showed four chicks. So I guess that we will never know what happened but the good news is that it appears that there are 3 very healthy and well fed chicks here with their beautifull parents and that there are regular feedings.