I have two 4-5 week old chicks that I've had almost 4 weeks. Since the day after I got them they have been sneezing with on and off bouts of congestion/wheeziness. They're growing, eat and drinking like normal other than the sneezing. The lady I got them from said she had URI infection going around her adult chickens but that these were probably fine because they were inside in a brooder. She said if they did have URI that it would run its course but we're now going on almost 4 weeks of this! I've been using Vet rx, they get vitamins and electrolytes daily and I started to do a round of Tylan 50 but then read some scary posts and decided to stop since they're acting completely normal. What could it be/how do I treat it?