I too had a really high death rate on my breeding colony when I first set it up. Seems some roaches just don't take the trip well. Took prolly around a month or so and then the die off quit. I didn't change anything and everything was right from the start. I did pick up around 50 adult females locally off Craigslist and they all were fine. Like I said, I believe some roaches just don't handle the long travel well. Also I don't think the protein thing in the chow did it. I feed mine Scratch and Peck organic soybean and corn free starter chick mash which is 21% protein and they love it. It's pretty cheap($32 for a 40lb bag) and will last forever as long as you don't get it wet. The breeders have been having babies all over and the feeders in my feeder bin have actually begun to outgrow the feeding size I need them so I've had to throw them back into the breeder bin and pick out the right size I need from the breeder bin.
Also can feed your breeders white bread. Mine love it and go completely crazy for it. The babies all run out and all over when I throw in 3 slices as well. Also I feed em grapes, brown parts of bananas, apple cores, left over beardie food, dandelion greens, collard greens, mustard greens, romaine and green leaf lettuce. Pretty much anything that is safe for you and your beardie they will eat. I try and limit the feeder bin to just stuff I want my beardie to get into her system.