My flock of 16 chickens seems to have a respiratory infection going on. We introduced 6 new birds to the flock last week and they seem healthy but the established group seems to be sneezing/ coughing and have yucky eyes that have bubbles in them. There is no smell as of yet with them. I have been doing lots of reading and it sounds like it could be coryza or mycroplasma. How do I tell tbe difference? They seemto be eating and drinking well. A vet visit is not an option.......I really do not want to kill off the entire flock.