could my 5 week old cornish cross have bronchitis?HELP

my cor rock cross chickens are 5 weeks old and mostly feathered, i put them out in the big coop out of the brooder at 3.5 weeks old.The new coop was being kept at about 55 60 degrees, and the birds have a heatlight with them. they appeared to be comfortable, however the next day i started to hear some sneezing, and about 3 days later i noticed some of them had swollen cheeks[not the waddles]. a local chicken farmer thought that it might be bronchitis and suggested using some duramycin, i started using it on sunday night, and here 3 days later there is still no change[but not getting any worse] is this information from the farmer correct?