Okay so someone placed an add for incubating eggs, I thought this sounded fun and I wanted to optimize this year's hatch, so I gave them 40 silkie eggs and 10 hatched. I went to pick them up and he took me in back to collect my chicks, the incubator was in a shed next to where his chickens were housed and some seemed sick. I had enough sense to be the one to take the chicks out of the incubator and disinfect my shoes but I did not have enough sense to consider airborne pathogens and quarantine the chicks, instead they went with a hen and her newly hatched brood outside along with all my other birds. A week later, April 1st, the chicks began to sneeze and flick their heads and since they had been around my other chicks they now all sneeze, I have nearly 50 sneezy silkie chicks now. I should note that I have yet to see enough sneezing from my adult birds to suspect they are sick though it is possible they are ill and just so asymptomatic that I am not seeing them as sick. I have been raising chickens for 20 years so I can safely say that there was nothing about their housing to account for sneezing, they are housed exactly like all my past broods. So I knew they were sick and not allergenic, I have dealt with a lot but never respiratory disease before, so I hastily sought help from a vet. I took them to the vet the very day they started sneezing, the vet prescribed duramycin-10 for the entire flock for 2 weeks (a tablespoon per gallon) and gave me some pink antibiotic liquid to give twice a day for anyone that was sicker. Of the 10 incubator chicks 2 would mouth breath on occasion but only for a few moments at a time and only after a hefty sneeze or when trying to sleep, they were also the only ones to sneeze loudly, so they got the pink stuff; I should note that both chicks seemed a touch weaker from the start and one had a rough navel. On April 6th I saw some red mucus in their otherwise normal poop, a fecal test revealed nothing and the problem quickly subsided, we suspect intestinal shedding from the antibiotics. After a full course of antibiotics and daily feasting of scrambled eggs and lots of TLC I have seen zero change, they are just as sick as day 1. It is now April 17th and they are exactly the same as April 1st, just sneezing, head flicking and sometimes slight heavy breathing with their beaks closed. Aside from occasional open mouth breathing from the 2 chicks I have seen no other symptoms, not even droopy wings or being puffed up, no one ever actually acted sickly. There is no nasal discharge, no facial swelling, no neurological symptoms, no eye problems, no coughing, no wheezing, no droopy behavior, no abnormal poop beyond that odd occurrence April 6th. All of the chicks have been growing and developing perfectly normal, they jump and play, they are little piggies about food, aside from these consistent sneezy symptoms they otherwise seem perfectly normal. The vet seems unable to tell me what the heck this ailment is beyond being "likely a virus that has to run its course" does anyone here know what this could be? Can anyone here tell me I can quit worrying about my birds now??? I have been extremely upset with myself for not quarantining the incubator babies and worried sick I that I may have brought something deadly home. TDLR: 50 chicks under a month old have been sneezing and head flicking for 17 days, the only other symptom seen is occasional slight heavy breathing with their mouth closed and 2 weaker chicks doing some open mouth breathing, otherwise they are active and eating and perfectly fine, what is wrong with them?