I'm new to chickens. Have a beautiful partridge rock rooster who's about four months old. He didn't leave the house this morning. I thought it was because the weather is so weird today. I went to get him to eat his supper and he didn't appear to be able to stand. Finally, I sat him on the ground. He made some wild dash to the other side of the pen and collapsed in a heap. Holding his head steady. Slightly loose bowels. No blood. He's been fine up until now. I purchased him from an individual who'd hatched him from eggs bought online so I assume no vaccinations. What do you think? I've isolated him. What about the chicks with him? They are younger. Will they get this too? I am new to this and appreciate any input/suggestions.