Urgent/Chickens Dying/Need Advice

1) What type of bird , age and weight (does the chicken seem or feel lighter or thinner than the others.)
The current chicken that is sick is a four year old Ameraucana. She seems a lot thinner than normal. Her breast bone seems to have no meat on it.
2) What is the behavior, exactly.
Lethargic. She has poop all over her but. She seem to have an air sac full of air where we clean the poop off. She was eating a drinking until today.
3) How long has the bird been exhibiting symptoms?
5 days
4) Are other birds exhibiting the same symptoms?
Yes we have lost two other birds. We have a flock of 12 left.
5) Is there any bleeding, injury, broken bones or other sign of trauma.
no.
6) What happened, if anything that you know of, that may have caused the situation.
We do not know of anything.
7) What has the bird been eating and drinking, if at all.
Prior to today the bird was drinking and eating. We feed organic lay pellets with a mix of five grain scratch. In addition, they get meal worms as a treat and they are let out periodically to peck in the yard. We have a five gallon waterer that has garlic and vinegar added to the water. We have also been putting out another waterer with electrolytes and probiotics in it since the chicken has become ill.
8) How does the poop look? Normal? Bloody? Runny? etc.
Some white and more runny than normal. We have not observed blood in any of the stool thus far. It gets stuck to the chickens butt. We clean off all of the poop, but it happens daily.
9) What has been the treatment you have administered so far?
Providing electrolytes and probiotics in a separate water container. Garlic and vinegar in the water. Organic Durastat(contains oregano) in another water container. We have also given the sick chicken Nutridrench.
10 ) What is your intent as far as treatment? For example, do you want to treat completely yourself, or do you need help in stabilizing the bird til you can get to a vet?
We are concerned that two birds have already died(within the last month) and would like to treat here if possible. We don't think the current sick chicken will make it, but are concerned that the rest of the flock will get whatever it is she has.
11) If you have a picture of the wound or condition, please post it. It may help.
12) Describe the housing/bedding in use
The chicken coop is a 25x10. We have multiple nesting boxes. We provide diatomaceous earth for the chickens to dust in. We have put dried herbs in the nesting boxes. We use pine shavings in the nesting boxes.

 

Upon checking on her this afternoon the "air sac" has seemed to go down. This is what her butt looks like now? Do you think this could be vent gleet?

 

It is inflamed and does have a strong scent. What do you recommend to help her other than that? She is extremely lethargic. I gave her some NutriDrench.