The only way to know for sure what is going on with these chicks is to take a very sick chick or a dead one to a state animal testing lab for a necropsy. Call you state agricultural office for the location of one nearest you.
If this is a virus, Marek's is a possibility, an antibiotic will do no good. If the chicks have been scratching around in the local soil, it could be coccidiosis. You would treat with a coccidiostat, the brand name depending on what country you live in.
There is also a chance this is something toxic or poisonous. Have you noticed any strange insects near the chicks. Some can have a neuro- toxin that can kill a chick quickly.
Mold exposure can produce the symptoms you describe as well as paralysis. You must be prepared to do some investigation to see if there is something dangerous such as a toxic compost pile or a machine leaking fluids onto the soil where the chicks have been hanging out.
If this is a virus, Marek's is a possibility, an antibiotic will do no good. If the chicks have been scratching around in the local soil, it could be coccidiosis. You would treat with a coccidiostat, the brand name depending on what country you live in.
There is also a chance this is something toxic or poisonous. Have you noticed any strange insects near the chicks. Some can have a neuro- toxin that can kill a chick quickly.
Mold exposure can produce the symptoms you describe as well as paralysis. You must be prepared to do some investigation to see if there is something dangerous such as a toxic compost pile or a machine leaking fluids onto the soil where the chicks have been hanging out.