the post about poisoning brought up a very interesting idea to me. What if they were slowly poisoned by something or something was affecting their minds.
for example:
"Ergotism, or ergot poisoning, is when a person or animal eats food that has been contaminated with a fungus called C. purpurea. The fungus is most commonly found in rye, but it can affect other grains and grasses, too."
and
"Ergot is a fungus blight that forms hallucinogenic drugs in bread. Its victims can appear bewitched when they're actually stoned. Ergot thrives in a cold winter followed by a wet spring. The victims of ergot might suffer paranoia and hallucinations, twitches and spasms, cardiovascular trouble, and stillborn children."
I am not saying it was Ergot but that might explain the things they did (if they did them) that do not make sense. Setting up the tent and not the stove, not enough firewood, the Labaz being in the ground instead of above ground, the lack of consistent entries in the diaries and/or change in the way they were written, cutting out of a tent due to paranoia, not dressing properly etc