Help sick chickens
Can you take one to a vet to have tested.
Can you post photos of the combs, legs and whole body?
Sounds like a respiratory illness. Does the discharge smell?
How old are they?
There are several respiratory illnesses with symptoms similar to what you describe. Depending on which illness it is you can give supportive care with antibiotics, but most illnesses will make the birds carriers for life, meaning the illness can be passed along to any new birds that you introduce to your property/flock.
Here is a list of the most common illnesses: