The coir does have nutrients. It's part of the plants (coconut fibers), just like veggie and fruit scraps you feed your worms. Check the link for nutrient analysis. Pre-digested coir have a habit of binding calcium and magnesium, preventing uptake for the plants. I don't know if they still do it after digested by worms.

I'm not sure about cardboard's nutrient value. I'm assuming it has very little, if not nothing.

I'm sure you already know, but the worm castings are best if it has many variety of food scraps, for higher quality and balanced nutrients available. Next time, throw food in before they chomp all bedding! :)

Here is a link that might be useful: Nutrient Analysis of Coir (PDF)

Okay, thanks Aindra, and thanks for the link, too!

Cornstarch is the 'glue' that holds cardboard together so it probably has some nutrient value.