Most of them seemed healthy when I opened the box this afternoon, but every time I go check on them, another has collapsed into the water. I'm using the standard mason jar waterers I've used for my last 4 batches of chicks with no previous issues. I'm not sure if the symptoms are useful, since it could just be inhalation pneumonia, but they can't lift their heads or open their eyes and they lay there with their legs stiffly stuck straight out, gasping. They flap and kick and cheep a little, like they're trying to stand up but can't. They've all died within an hour of me finding them ill. I euthanized the last one. 4 of the chicks were polish, the last one was a sussex. Any ideas? The rest are doing ok (so far) but seem less energetic than normal. They were vaccinated for Marek's and Coccidiosis at the hatchery. 2 of the chicks died in transit and the others were eating them. They also had gro-gel in the box with them. They've got electrolytes in their water now and I'm less worried about the ones who are managing to eat. I've never lost more than a single chick (pasty butt) from a shipment before, so I'm really worried. Does anyone know what it might be? Are the rest likely to die?