I've lost 2 seemingly healthy hens (2yr old and 10 months old) in the past 3 weeks. There were no obvious causes of death (trauma/sickness/change in behavior/featherloss...). The rest of the flock is peppy as ever. I've had hens for the last 2 years and no problems like this. Been feeding the same laying pellets and scratch. I have 2 roosters in the coop could they be doing this? Or do I need to worm/vaccinate? Any other ideas?