I recently got 3 new 3-4month old chickens. They all got a respiratory infection which then passed on to my old 6 month old flock (despite keeping them separate) so I've been treating both flocks with tetracycline 400. Recently I noticed in the new chick pen that there was bloody (very bloody) poop in there. One of them is shaky and the other quite tired and lethargic looking. What do I do? I don't want it to get passed on more so to my old flock and want them to get better! The breeder dos not vaccinate my new hens.