I practiced vermiculture composting for a couple of years, so I am far from a pro. Here are my thoughts though.
Don't change a thing. If the worms aren't all conducting a mass exodus there is no issue. If you are wanting to use the casting/compost now and that is the issue you can take out what you need bit by bit and use it where you want. You'll be removing some worms when you do this, so the terrible result is that wherever you use the compost you'll be adding worms as well (OH NO!!
I used a 5 bin system (holes drilled in 4), with the bottom as my worm tea collector. I am assuming you are using a similar system. What I observed is that as long as the worms are still in an area they are still using it. I would leave each layer alone until there were very few worms left in that layer. My worms seemed to like to lay their eggs(little white orbs) in the lower levels so by leaving them as long as possible your worm population will increase exponentially. If you are adding that much material and they haven't finished eating the first layer I would say you don't have enough worms yet, so removing any unhatched eggs could actually hamper your overall progress with the colony. Once I had a lot of worms in every layer, (by that point my bottom bin was pure black muck) I started adding it to my potting mix, this would add worm eggs/worms (you'll never get them all out, but once your colony size reaches a certain point it will have no effect on it) to my seed starter mix, which would be grown indoors and eventually be transplanted out in the garden. By doing that it accomplishes many different beneficial things for very little input. Another thing I did was add some of my finished compost to each layer to let all the microbiology do its thing (I have no facts to back this one up, it just makes sense to me...)
The other thing you could do is just split your bottom bin between all of your other bins and add more dry material. Really though if there isn't mold and stuff growing all over and your worms aren't leaving I'd say there is nothing wrong. After about a year with my worms I got an old blender from a garage sale and started making "worm smoothies" every time I fed them. It allowed the material to be eaten a lot faster, but it'll also allow it to compost faster as well. I overfed them and that is exactly what happened to me, You'll know something is wrong when you see a few thousand worms climbing out of the bin lol. To fix it I just scooped out all the leftover "food" and a bunch of the dirt and just mixed in fresh dry bits. After that was sorted I continued using the smoothies and made sure they were keeping up to what I was feeding them.
I had my bins indoors in a 40% humidity environment in my grow room which has a dehumidifier set at 40%. I am not sure how much the humidity level will effect the bins.
Oh yea, I didn't buy the worms either. At 20 bucks plus shipping for 1 pound of worms I said screw it, walked out to the garden, flipped over some leaves, grabbed the worms that were in there and used those to start my colony.
Hopefully that helps.