I would stop the 30% gamebird feed at some point, because feeding that high of protein can lead to gout which may cause swollen joints and kidney damage. 20% protein is about as high as I would go on protein. Scratch has about 7%, contains a lot of carbs and fat, and they will eat that over any...
What exactly are you feeding including any extras? I would consider worming them with Valbazen or SafeGuard liquid goat wormer in case of worm problems. How are you treating the mite issue? You will need to get permethrin dust to treat the chickens, and permethrin spray to treat the premises...