it would be a good idea to use at least 2 feeders/waterers so everyone has access, in case she is at the bottom of the pecking order.
It is also possible that one of the others pecked at her eye, and it swelled up.
what about poops? are they normal/runny/green? any blood or small red bits in it? that would be a sign of cocci. which would be consistent with being sluggish, not moving, eating less etc. That also kills quite fast, and if she has it, they probably all have it. You can take a poop to the vet for testing (any vet will do it, will cost 25-30 dollars) and you'll have results within 24 hours, or you could buy Corid and just treat them all.
Here is some cocci info here:
Coccidiosis Treatment
There are many forms of Coccidiosis, but two main ones are treated, these are Cecal and Intestinal
Coccidiosis in chickens is caused by seven different species of coccidia (genus Eimeria), which are single celled parasites that live in the gut wall of their host. These coccidia are host specific: turkeys and other species are not infected by fowl coccidia and vice-versa. The different species of coccidia live in different parts of the gut and can be divided into those causing intestinal coccidiosis (the majority) or caecal coccidiosis (one species).
Coccidiosis Cecal Symptoms
In chicks or young birds, droopiness, huddling with ruffled feathers, loss of appetite, retarded growth, and bloody diarrhoea in early stages
Mortality is high
Spread from contact with droppings of infected birds. Spread on used equipment, feed sacks, feet o humans and wild birds
An important symptom is blood around the vent or bloody diarrhea
Unfortunately, many different diseases of chickens show identical symptoms which makes accurate diagnosis very difficult
Coccidiosis Intestinal Symptoms
Affects growing or semi mature birds, droopiness, huddling with ruffled feathers, loss in interest in water and feed, retarded growth or weight loss, watery, moucousy, or pasty, tan or blood tinged diarrrhea, sometimes emaciation and dehydration
In mature birds; thin breast, weak legs, drop in laying, sometimes diarrrhea
If affects their intestinal tract
Mortality is limited to high
Spread from droppings of infected birds; spread on used equipment, feed sacks feet of humans and wild birds
An important symptom is blood around the vent or bloody diarrhea
Unfortunately, many different diseases of chickens show identical symptoms which makes accurate diagnosis very difficult
Treatment:
1-teaspoon amprolium (20 percent) per gallon drinking water for 5 days (this is not an antibiotic)
Also a broad spectrum antibiotic to guard against secondary infections, ask your vet what they have available
Following this treatment, give multi vitamin supplement (especially A and K)
Survivors are immune by may never be as productive as uninfected birds
Spread of the disease
Damp or contaminated litter and overcrowding favour its development.
Most commercial chick starters contain a drug that inhibits coccidiosis, however if a clean, dry environment is not maintained then disease can occur. Birds fed diets without preventative drugs are particularly at risk so clean dry litter and adequate space are especially important
If you have soil in your coop it would be advisable to turn it, but don’t allow dust to blow everywhere, as this will spread the disease, if you sprinkle hydrated lime into the soil it will help to eradicated the problem… make sure no lumps are on the floor, use a flour sifter to apply it and then rake it into the dirt
Coccidiosis is spread when one bird eats faecal material from an infected bird, which contains the infective stage of the coccidia (small egg-like bodies called oocysts). The oocysts in the droppings need moisture and warmth to mature before they can infect other birds, but in the right conditions, can do so very quickly (24 hr). Oocysts can remain alive in poultry sheds for more than a year and they are very resistant to most disinfectants.
Oocysts are ingested when birds scratch and peck at the litter or consume contaminated feed or water. Each oocyst breaks down in the gut to release eight organisms that invade the lining of the gut. They then multiply through several cycles to produce thousands of parasites, damaging the gut and causing disease that may lead to the fowl's death.
Beginning five to seven days after infection, thousands of oocysts pass out in the droppings of the bird to continue the life cycle. It is impossible to prevent this spread unless birds are housed so that they have no contact with faeces.
