I am just chiming in because this looks interesting, but Wyorp Rock is doing a great job with her suggestions to help you. It looks like all 3 chickens have an irregular pupil in the photos, which could be better. Irregular pupils can be an indication of ocular Mareks, but isn't always. Some chickens and other birds and animals can have a coloboma, which is a keyhole shaped pupil. It's strange that all 3 would have this irregular shaped pupil, and you may want to contact a state veterinary school or vet that may help you. Casportpony, a BYC member who has Mareks in her flock, has sent others' photos off to a vet she knows in California of chicken's eyes for an opinion. You can get some good pictures and PM her in case that might be something she could help with.