This may help you
How to Keep Crickets Alive Longer :Guide to Breeding Feeder Crickets very good article and down below about virus that affects crickets, that is I think your crickets have.

However.... No matter what you do you will have smell and deaths. A lot! I never buy more then I can use in a week, 250-500 at a time lol about 20-25% will die anyway.
Another thing to consider, these cricket keepers are horrible, just get a plastic bin, cut off window in a lid for ventilation, glue mesh ( I use window screen), place a lot of egg crates, water gel and some food. Place them in a warm, dark place.