If you see any of the comma ones turning dark, they are pupating, so feed them at once. This might sound like a hassle, or even dangerous, but it doesn't have to be if you're careful. After awhile, you may get the choclates to eat a good flake food if you squirt it past them with the baster. Earthworms are a great food too. Perhaps the smell will tempt them.
Grindal worms are a dependable year round live food as well.
Check the Krib for more on these.