I'm in need of some help. My flock began with 6 sex link hens which are now about 5 months old, and we added 4 Rhode Island Red hens which are about 3 months old. Two of the Rhode Island Reds died when they were about 1 month old, and another died when it was about 2 months old. Two of the three acted lethargic the day prior to their death (i.e. not wanting to walk around and not seeming overly interested in eating or drinking). 1 of the sex link hens died when it was 5 months old, and was acting very similar. It would just sit on the ground, and I even watched the other sex links stepping on it. I haven't changed their food, they get fresh water daily, and I haven't noticed any other symptoms of illness. This seems to come on fast, and they are typically dead the next day in spite of my efforts to more closely attend to them. This is my first time raising chickens, and I am at a loss for what's going on. Can anyone give me some advice/ideas? Thanks in advance.