Was it also humid? I used to have lots of dead crickets, i found that using empty toilet paper rolls stacked one on another lets air move around better. Rather than them all cramping up under an egg carton.
Yeah, they suffocate. Just like when you put to many of em in a box.
I have every one at work bring me all their empty toilet paper rolls. I can put 500 crickets in a medium size critter box with hardly any deaths.
Try it out, it keeps the bottom of the box dry and clean.
yeah, they are most likely almost dead. i would just get the ones that are moving around normally and let the others die that are on their backs or look weakened. then buy some more and start fresh, because humidity is a place for bacteria to breed, so make sure the container is super clean. i usually put in a little bleach and let it soak then rinse it out good with water and soap.