I don't know whether this helps, but RUSKS are mentioned by several witnesses, and rusks are bread. A bag of them was probably accidentally cut open by Sharavin and Slobtsov when they first hacked into the tent with the ice ax. If you search for RUSK using the search bar (not here in the forum but out on the main DyatlovPass.com website), you should be able to find all the witness statements that included that term. But no, poisoned bread (or mushrooms, etc.) could not account for the mystery, because the nine left the items orderly in their tent, and they walked in an organized manner down to the trees, and gathered many branches for the fire and the snow-dens, and did many logical things.