did I gather this was a old english bantam?
well do you know if the chicks came from a healthy flock?
that flock never ever had the respiratory disease?
and recovered from it?
thus it is in the chicks
BUT NOTE THIS
has people been coming to your house and handling the chicks?
if so they could have brought the disease on their hands from some other flock that were carriers for this repiratory disease
biosecurity is important
don't go near other chicken peoples chickens
or let them come near yours
with all that said you need to get on it to help your birds with their gut flora for fighting the diseases
also take and 2 parts clorox to 10 parts water and clean all the feeders and waterers
if you got oxine then use it to cleanse them
and spray the whole flock with oxine
do so at night way over their heads so it flilters down
you can get it from first state vet
then do the wet mash with vit's for health problems
natural probiotic recipe is :
1 qt of dry crumbles
2 qts of milk, sweet, sour, or buttermilk or a mixture of all or some
1/4 cup of non flavored yoguart ( no artificial sweetmer)
mix good
NOW THE IMPORTANT INGRIEDIENT FOR EACH CHICK FED
and add 1- 1000 mg of Vit E by cutting the end off the vit E capsule for each chick fed this wet mash
and 1 seliunium tablet crushed for each chick fed this wet mash
putting it in the wet mash
this for each chick your treating
so for each chick use 2 tsp of mixture and 1-1000 mg of Vit E
and 1 sleinium tablet crushed in the wet mash probiotic
twice a day for them till the manure is solid
Feed what they will clean up in 20-30 minutes
then clean wet feeders and restock dry crumbles
do this twice a day for a week
then quit the Vit E and selinium make just the wet mash probiotic
then once a week for life
if not medicating the birds use
Apple cider binegar in waterers
do not use ACV with medication
2 tbsp of apple cider vinegar per gallon of the chicken water so their gut flora wil be regulated
they should have this at least 3-5 days a week
the vit's are neccessary to clean up the damaged gut problem