We recently (2 weeks ago) bought a flock of 23 two year old Plymouth Barred Rocks. They are such nice birds. A few days ago we noticed especially that one bird was looking sick and had white diarrhea sticking to their feathers near it's vent. It started getting lethargic and just looking generally sick. It's vent was pulsing and red and it looked like there was a scab or some sort of sore hanging off it's vent although now I think it may be something blocking the vent. Yesterday that chicken died. When it died, we noticed that there was blood in it's vent with some poop but we did not see this in any of the poop in the coop or yard. Since that one died we have noticed that there are some other chickens who seem to be exhibiting the same symptoms. We think it might be cococcidiosis but I thought it might be worth checking on here for some other advice. Because they are older I know it's not necessarily likely that they have it but it seems like the symptoms fit. I have been checking the poop in the yard and I haven't found anything with blood but some of them look like caramel colour. Any adivce would be helpful! We would really like to keep the rest of the chickens from dying! Thanks!