OK, question. I purchased seven three month old pullets (I'm new to this) from a local well-known supplier about a month ago - I have three surviving - 3 of the original showed no symptoms of anything (eating, drinking, running around), just found them dead in the run. The first was 3 days after purchase, the 2nd was a week or so later, and the third a few days after that. Right after the last death I started a broad spectrum antibiotics in their water for 10 days. About 7 days into the antibiotics one of the surviving pullets got a swollen eye - I thought initially it was the RI red picking on her. I separated the red from the flock to put her in time-out for a few days to "take her down a notch" - no improvement in the eye of the other chicken. After research I started suspecting eye worms instead of bullying (no respiratory issues at that point), bought vet RX, treated on roof of mouth & in eye, slight improvement but no significant change. I was also treating the entire flock with Oxine in a vaporizer for about a week every night with no improvement. The swollen eye bird started to smell - more research - pulled her from the flock 2 days ago & she died last night. On her last night she was "pump handle breathing" and had a whitish discharge around her beak.
This morning a second pullet has a red, sticky eye - not as swollen but not normal either but no other symptoms except for a very occasional sneeze - I pulled her from the flock immediately. (It should be noted that this pullet did have a swollen eye at the same time as I was treating the first sick chicken for what I thought was eye worms & her eye recovered quickly after 2 treatments with Vet RX - the now dead chicken never improved.)
So, I have 1 dead pullet, 1 sick pullet in isolation, and 2 pullets left showing no symptoms that, because of my lack of knowledge, were exposed to an actively sick chicken for about 2 weeks. After reading these threads I'm thinking Coryza because of the smell that the now-dead pullet had (the newly sick one is not showing this symptom yet) but I'm not sure as I understand that it does not have a high mortality rate. I understand that if it is Coryza that the bird will be a carrier for life & I'd rather cull her than take a chance if this sounds like Coryza to the forum experts. The other pullets "dropping dead" could or could not be related but I have no idea.
My real question is: Does this sound like Coryza? If so, do I assume that the 2 "healthy" pullets are carriers and cull them also or so I assume they were lucky and never got infected? Is it possible for a chicken (or two) to be in a coop with a sick chicken and never get sick? Is it possible that the two "healthy" pullets did get sick but didn't show symptoms or would it have been obvious? Obviously a flock of two is not ideal and I'd definitely want to restock but don't want to go through this again nor do I want to cull two perfectly healthy chickens...
I'd really appreciate any help you could provide. Thanks!