I'd like to see your brooder setup please.This is them in a carrier when i was disenfecting the brooder
Can you please post photos of the chicks, poop and brooder setup?
I'd go to TSC and get some Corid, it's in the cattle section.
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.
Where did these chicks come from?
I'd get them off the gamebird starter and onto Chick Starter.
What are you disinfecting the brooder with?
Edited to add. I see you're asking about how to send a bird to your lab. You'll need to look up your state lab and contact them. If you lose a chick, wrap it in plastic and refrigerate it so the body is preserved until you can get it to the lab.
https://www.metzerfarms.com/poultry-labs.html
Please post clear photos that are well lit of the chicks, their poop, the brooder.
Please tell us the temperature of the brooder on the warm and the cold side.
Gamebird starter feed is around 30% protein, so it should be o.k. for chicken chicks for a month or so, but I would not feed it longer than 2 months.