Cornmeal should be fine for the worms if sprinkled over the bedding in small amounts over several days. I would question whether baking powder is something you should be feeding to the worms, since self-rising flours contain baking powder.

You would also want to check the ingredient list to see if there is salt in the corn meal. Some of the regulars here are not concerned about small amounts of salt, but I will not feed my worms anything with salt in it.

If you can eat it, then the worms can eat it when it rots.

Salt doesn't rot.

True.
As you wish.

In fact, salt is a preservative. It kills bacteria.

You know, for years I have been telling my wife I was going to get some "T" shirts printed.
On the front it would say,
"You're right, and I'm wrong"
and on the back it would say,
"I'm sorry I even mentioned it."
I could sure use one now!

I'd buy one.