I found a couple of great articles from Kevin Dunn (
Scientific Soapmaking) that are applicable to my DOS issue.
The one he wrote about DOS was an eye-opener for me, particularly when you see that superfatting really isn't the issue. I wondered about the 20% superfat being the culprit, but that didn't make sense because that seems to be fine for coconut oil. It appears that using a lower superfat won't prevent DOS or cause it if you use a high percentage. In his experiment, a 0% superfat soap was compared to a 10% superfat soap. Both got DOS at the same time, although the 10% superfat soap showed more color over time. Even more interesting is that he found that coconut oil is pretty resistant to DOS. Since my soaps were 100% coconut oil, I read on to another of Kevin Dunn's articles on water discounting, and think I've found the culprit.
If you look at page 3 on the right side under the heading, "Coconut Oil Soap," Dunn notes that coconut oil soap holds on to water longer than the palm soap it was compared to. "Because coconut oil soaps take longer to lose moisture than do palm soaps, the advantages of using less water are more pronounced for these soaps."
So there were my poor little soaplings, birthed with full water, gasping for air and drowning in their little plastic prisons for a full week. Add in some high humidity and they probably never had a chance. Both articles are well worth the reading, and I'll be purchasing "Scientific Soapmaking" very soon.