Chickens don't get colds, and corid is not an antibiotic, it acts inside the cocci to block their thiamine uptake. She could have any of several respiratory diseases that chickens sometimes get, though. You would need to know which one to treat properly. The best route would be an avian vet, of course, but most people on here find that too expensive. The wheezing could be something caught that will pass, gapeworm, or any of a number of other things. I would look inside her mouth to see if you can wee any worms; gapeworm is easily seen this way. You could get an antibiotic from the feed store -- some are tylan, sulmet and baytril -- if you want to gamble that you will pick one that will help. However, most chicken resp. diseases are viral, and no antibiotic kills viruses. If she has a resp. disease, the others will also most likely get it. The droopy comb is simply a symptom of being ill, probably a little dehydrated, and the pale color probably indicates the area is not getting enough oxygen, possibly from a respiratory problem. Another possibility is that she has a heart problem which is causing both the wheezing and the pale comb.
Not really much help, but gives you a little overall info. I don't know anything specific about these resp. diseases as I have never dealt with them. In many places there is a govt. agency or university that may be helpful; you could contact your county extension agent to see what might be available locally.
