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Quite a large crop on that one. A gagging motion is an attempt to adjust the crop.
Check to see if their crops are emptying overnight. Do you provide grit (crushed granite)?
If possible, get a fecal float to see if worms and Coccidiosis are part of the problem. If not, then I'd treat their crops, deworm and treat for Coccidiosis.
Corid to treat Coccidiosis. Liquid Corid is 2tsp or Powdered Corid is 1 1/2tsp per gallon of water given as the sole source of drinking water for 5-7 days. Treat all that are housed together. Don't add any extra vitamins or supplements to the water during the course of treatment.
Safeguard liquid goat dewormer for deworming. Dose is 0.23ml per pound of weight given orally once a day for 5 days in a row.
What protien% is the grower feed? I'd keep the youngsters on an 18-20% starter or all flock feed until they mature and come into lay. Then you can switch to a lower % layer feed (Layer feed is usually less protein than most, but contains more calcium than youngsters need).
If you have different ages, then feeding an all flock (18-20%) feed or even chick starter will be easier than having to try to feed separate feeds. Once everyone is mature, then you can switch everyone to layer feed if you wish. Provide oyster shell free choice, the laying birds will pick up what they need.
The article addresses the crop
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/