Background: One of my pullets died Sep 9, necropsy showed lymphatic tumors and pneumonia, possibly Marek's. Current question is about a different pullet. Pullet, 20 weeks old. Sep 20 lethargic, wheezy, isolated with antibiotics (Sulmet). Recovered with 2 days treatment. Sep 22 returned to flock, closely monitored. Sep 25 lethargic again, head shaking, droopy wing. red mites noticed, entire flock treated with BioSpot. Head shaking stops. Isolated for rest overnight with probiotics and electrolytes. Sep 26 Seems recovered, returned to flock, entire flock provided probiotics and electrolytes. Pullet is eating and drinking. Sep 27-28 head shaking returns. Lethargy returns. Eating and drinking is minimal. Sep 28 (today) isolated from flock again. What am I missing? I haven't noticed irregular poop, so I haven't dewormed the flock. In isolation, she seems to stop eating and drinking, while outside with the flock she at least tries. This is my favorite bird, and I will do anything I can to save her. Please share your ideas with me!