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You've only had them for a couple of days?
Likely the feather loss is from overcrowding and picking. Chicken skin can look red when it's exposed and pecked.
I'd cut out all the sunflower seeds and scratch. Provide them with a nutritionally balanced poultry feed in a feeder. You can give a small amount of the sunflower seeds/scratch/corn a couple of times a week or better yet, give them small treats of egg, fish (sardines, mackerel, tuna) to help boost protein.
Feathers are picked and broken. Once they molt, then those feathers will be replaced.
Once you've had them for about 2 weeks, I'd give them a round of Corid for Coccidiosis, then deworm them with Fenbendazole (Safeguard) or Albendazole (Albendazole).
Liquid Corid dose is 2tsp or Powdered Corid Dose is 1 1/2tsp per gallon of water given for 5-7 days as the only source of drinking water.
Do not add any extra vitamins/electrolytes that contain B1(Thiamine) to food or water during the course of treatment.
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Safeguard dose is 0.23ml per pound of weight given orally once a day for 5 days in a row.
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Valbazen dose is 0.08ml per pound of weight given orally once, then repeated in 10 days
Here's how to give oral medications:
https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/