Ok so I am still fighting this same bug or whatever it may be with my week and a half old babies now. I already lost the little maran, but I still have 2 americaunas and 2 wyandottes left. I really don't think it's contagious, because I had my older silkies right beside them in the other brooder and they were just fine. It's not the bedding, it's dust fee, there isn't a draft, they are in the garage, not the temperatures, I have 2 lamps on them and a thermometer in with them, the food is good quality food and they also get other snacks, so it's not nutrition. The remaining 4 aren't sickly, but they aren't 100% either, I keep seeing them breathing heavy and sometimes they pant, but they hop around, eat and drink well, play, grow and act like normal chicks do. They don't sneeze, wheeze or have any crusties on nose or eyes, but the one that died didn't look bad either and even had a full crop the last day. This is scary! I have had them on tetracycline for 5 days now and they are still exactly the same, I don't want to suddenly take them off it before the cycle is through in case that there is something lurking, but I was wondering if I can try adding an antibacterial to the water also. I got some sulfamethazine sodium that I would like to try giving and see if that would work. I have looked everywhere online to figure out what's going on, there is nothing even similar I have come across, yes plenty of respiratory stuff, but my guys don't have any other symptoms other then the heavy breathing, nothing fits.