Hmm my guess is temperature issue. I have had the same colony going for years. I use shoe box rubbermaid containers and keeps the worms in about 2" of wheat bedding.

Once they pupate i used to give the pupa they're own container but now i just throw them in with the beetles. So my setup it kind of like a hatchling gecko rack (its actually one i never finished )

I keep 5 tubs high by 4 tubs wide. Top level is beetles which i change they're bedding every 3-4 weeks. My system allows me to just move they bedding from the beetles to the next row and so on all the way down so i have fresh bedding with eggs and at the bottom i have my oldest worms that pupate. Keeping beetles alive mean keeping them hydrated. So water crystals for potatoes.giving the worms water is good but not as important as the beetles.

Good luck keep reading and check your temps. Mine stay around 80