I wouldn't if I were you. They're too small. It would do harm than good.

28 days is getting into the time frame of "concerning" but you just might have to face it that they might not ever eat, and won't make it. Don't give up yet though.

I would try placing them (singly) in a very small container and if you can find some very tiny worms that wiggle a lot, put it in with the baby and give them some time.