You won't get many signs of that since their population is self-regulating. If there's not enough food the population will stabilize at a lower level.
But, they'll consume the bedding as part of their feed, although technically the microbes break that down and the worms eat the microbes. They don't have very big mouths so whatever they take in needs to be pretty small.
Also, you may already know this but, be sure to add some grit in there for them. I use dusts of sand, Stone, char, etc. They have a crop like a bird and need some hard particles in there to help break up what they eat.
Edit: never mind on that last point as I just reread the amendment list you're feeding them so you've got that covered.