I purchased 29 chicks from Murray McMurray hatchery. 15 silver dorkings, and 14 other breeds. I picked them up the moment they arrived at the post office and 4 dorkings were dead upon arrival. I've had them in a large jacuzzi tub in the bathroom- heat, food (with some chick grit), & water. Everyone has been fine for a week. Until 3 days ago when I found a dorking dead. Then another one a day later and today is the 3rd day in a row that I have a dead chick- this time a dark cornish. Anything I should look for? I've been watching these guys intensely and they all seem fine- running around, spread out evenly under the heat lamp. I did notice the ones that had died had an enlarged area below their throat- croup maybe? I tried to take a pic of it below: I'm thinking my next step should be to move them an enclosed room in the barn for some different air? I appreciate any input!