In no way am I implying that your guys are not exprienced keepers. I am confident you all are.
Just a question out of interest? In what enclosures did you have the Avic's. And how much ventilation did the enclosure have? Just a strip on top or grills on top and on the side?
I think the Avic's require very efficient ventilation and could this have attributed to their deaths?
I have this theory. I will try use an anology to explain it. Say that in Nature an egg sac of say 200 slings only 100 would survive due to the 100 others being 'weaker' and becoming much needed nutrients for the surviving 100.
So now in captivity (using the same imaginary egg sac) we seperate the 200 slings and place them in their own enclosures. Their survival rate might be 150 and result in 50 dying due to them being weaker but even with our fragile best of care. Thus there are 50 'weaker' slings among the 150.
What do you guys think?