I would check back with the vet to find out what bacteria they found or if they did a culture and sensitivity. It may or may not be coryza, because other infection could be causing the bad odor from the nostrils. If you get a diagnosis of coryza or MG, I would not add any new chickens to the flock , or give any away. It helps to have a closed flock with carrier diseases, so that it doesn't keep spreading to different generations.
