The adults look like fairly normal dead adults, if that makes sense lol. This would convince me it might just be doom from old age. If you start seeing younger nymphs die off as well then we will be in for some troubleshooting.

Also good news - the living adults appear to be meaty and of healthy size. The weaker individuals I've encountered are very gimpy, not fill-out, and don't nearly have the same length to width ratio. You females look nice and plump, and I LOVE love love love love the colors on them. I've been culling a lot of mine lately due to excessive darker females, I want to see more of those bright oranges in the females that reach adulthood like you have there. Perhaps 5 years of inbreeding from a single colony of 250 has allowed more of the darker phenotype to come out and less of the nice rich oranges. I've actually contemplated buying up some fresh stock from good colorful bloodlines to mix into my current colony...

Also: some constructive critism. I wouldn't let the hottest point of the bin get any hotter than about 105 degrees F, 113 is a little intense in my opinion. See, just like our reptiles and amphibians, an insect's metabolism is directly proportional to the temperature and each species has its own preferred range. I think B. dubia fare best at a temperature in the long term when they are exposed to overall temperatures in the 85-95 degree range. Roaches will actually thermoregulate to maintain ideal core body temperature, but if things are too hot you may literally be causing them to age slightly faster. Not saying this is responsible for dei-offs, but it might be partially contributing. They may grow faster when kept extremely warm, but this also results in faster death and temperature spikes may even cause infertility or death of the embryo. I think your 95-105 range on the bottom was more ideal to begin with, although keep that heat tape handy in case things chill out some in the winter or you need to add another bin down the road = )

Honestly, I think you just have some old roaches - a 10% die off rate after 3 weeks isn't too bad, you still have in excess of 150 adults and assuming a 50/50 split of males to females, if each female can produce even one litter you should be able to produce another 1500+ nymphs at minimum. I think you'll be okay, there is just no way to tell an adult's age prior to shipping and some old roaches surely got mixed in. Odds are you'll have some old timers and some freshly molted adults, and those freshly molted adults will keep producing and thriving for you for months.

It sounds like you are taking fantastic care of them. The only concern I had about adding supplementation is I sometimes noted excessive calcium in the diet occasionally leads to bad molts in some inverts. Not sure why, I have a couple of hypotheses, but since you are feeding a perfectly good diet its not necessary to get into it.

Continue to do what you are doing and give them more time to settle in and start producing babies for ya. Keep us posted on them, I'm sure they'll continue to come around for you! Don't get discouraged!

And I agree with Mark in that a single bad molt isn't a major deal, you'll get that from time to time. Usually the fellow roaches in the colony consume this roach or it just falls down dead to the bottom of the bin.

Mark - I'll send you a PM regarding my availability = )