Have you recently had a wet spell or have they only recently been exposed to dirt that would make coccidiosis more likely? My concern is that they are over the age when coccidiosis would normally be a problem and if there are no that indicate why they would suddenly be susceptible at this age..... like they have just been introduced to new ground and/or the weather has been warm and wet..... my gut feeling is that there is an underlying cause like Marek's Disease compromising their immune system and making them vulnerable to it. That would tie in with them being in poor condition, since you mention that they are skinny despite eating well.
No wet spell, they only moved out into the run/coop about 3-4 weeks ago. I did have to go back to the farm and replace a rooster with a hen 2 weeks ago, but it was the same farm...so I was told it should be fine to just swap them. It wasn't a chick from the same batch, but only about 2-3 weeks older than the ones I had gotten.
Honestly, I have a feeling they might always have had cocci. This morning cleaning out their coop was a much different experience in that their poop was solid and not a pile of jelly. They've always had jelly poop, which I assumed was normal for chicks.
We also blocked off the nesting box, which is where they've been sleeping, and replaced the 2x2 roost with a 2x4, and it appears like they slept on that all night.
Also, why do people do the shavings in coops? I assumed I needed to, but it was so much easier just lifting out the poop from the DE that I put on the floor.
