So over the past few months I've lost 3 young cockerels to what I think might be Marek's. All our older hens seem to be fine though. It's only the young roos between 10 and 18 weeks old who die. The first one had extreme balance problems and weakness, the second one had a severe respiratory problem and was wheezing, and also had a huge growth near his ear. The most recent one had a big, crusty cyst on his wing. No other symptoms, just died. I have one other young cockerel still out with the hens, he's 12 weeks and showing no signs of illness but I'm starting to expect that he will eventually die as well. Does anyone know what this could be? I'm going to have my husband do a necropsy on the recent rooster and see if he has tumors on the inside.