Sorry your birds are sick.
Here is what I would do:
#treat them for coccidiosis using a sulfa drug like sulfadimidin/trimethoprim or similar
# check them for lice and poultry mites
#check the coop carefully for poultry mites at night with a head light and remove all bedding also in nest boxes and treat everything in case you find any. They cause severe anemia and infection in poultry.
#deworm all your birds
#provide more coop ventilation
#have a necropsy done by your state vet lab in case you lose another
Here is what I would do:
#treat them for coccidiosis using a sulfa drug like sulfadimidin/trimethoprim or similar
# check them for lice and poultry mites
#check the coop carefully for poultry mites at night with a head light and remove all bedding also in nest boxes and treat everything in case you find any. They cause severe anemia and infection in poultry.
#deworm all your birds
#provide more coop ventilation
#have a necropsy done by your state vet lab in case you lose another