I just popped in for the first time to see what's happening on this thread. A person I've been mentoring recently had a series of 7 deaths with 2 to 3 month old chicks. The chicks were voracious and attacked the owner and food every time she went into the pen. They were confined to a pen and fed a very expensive, organic, chick starter ration. The deaths were coming frequently, every few days, so we took one to the state lab for a necropsy. The results came back negative to everything they tested for, but there was a note on the paperwork that the chick looked normal but emaciated. We started looking for other causes and eventually checked the date on this very expensive, organic chick starter. It had been on the shelf for over a year. Clearly some nutrient had broken down over time and the chicks were starving to death. Within a day of switching to the much cheaper, conventional feed the chicks settled down and guess what... no more deaths. All my birds free range from sunup to sundown and get lots of foods from various sources, so I've never seen this problem before. I try to get my birds on grass as soon as weather permits, even if that means digging up clumps of sod to put in their brooder. From now on if people ask for my help raising chickens and they raise in confinement I will always recommend using two sources of food and mixing them but dirt and grass is important too.