I have 7 week old chicks. A few days ago, I noticed one of them acting lethargic. I thought it was just sleepy at the time, I refilled the waterers & it joined the others for a drink. When I went to shut the door that night, I found it laying on its back in the coop. It was all but dead & it only lasted a short time longer. I just went out there & found another acting the same way! It just acts sleepy until you nudge it or pick it up. Doesn't resist contact at all until its picked up, then sqwaks a bit. I have no idea whats wrong or what to do. They've been free ranging some for the last couple weeks. Could it be something they've eaten? No visible signs of injury.