Skinny Chook dribbling brown fluid.

Suggestions please,it's a long story so please bear with me. Im in sunny spring time Australia and We have 7 chooks and a bantam all about 2 years old.A month ago after lots of rain and wet scratch mix one hen Spike got sick, with brown vomit / fluid with fluffed feathers, lethargic and closed eyes with very pale white pink comb, didnt think she'd survive, I picked her up,( all are used to it and quiet) and she puked brown broth I thought might be sour crop but doesn't have the bad smell, no lumps & has an empty crop. After a couple of days of vomiting, tlc then fresh food, seed, mown green grass, vegie scraps and sunny weather with the others she improved slowly. After 2 weeks she's very skinny, still not eating properly or with enthusiasm, she does a head shake & is very deliberate in her picking, so I have been tempting her with a teaspoon of fresh beef mince each day, but crop doesnt have much food in it of an evening like the others.
Poop is minimal, runny green, still with the others & goes out on lawn for fresh pick & a scratch in back yard. Comb now has ok colour tinged purple & floppy. Pen has lots of dirt to scratch in plus no longer muddy. The others are all ok. Has any one ever had a similar problem & had good outcome?

Thanks for replying Helen. No worms. Spike isn't eating the crushed laying mix, (corn oats chaff etc created for laying chooks )she shows little interest in gobbling anything, including the fresh lawn grass that the others like to peck and scratch up, they do fight over worms grass hoppers slaters and anything else they find crawling,even a frog I wasn't fast enough to rescue, scraps, fresh fruit veg doesn't interest her, raw ground mince was the only thing she took an interest in, it was the closest thing I had to a worm, so if I stop offering that I have run out of things she will pick at / eat. After 2 weeks of this I can't find anything to give her that she will try to eat lots of. Her crop is droopy and shes getting skinnier no longer vomiting but not eating enough either, still interested in wandering around picking not frenzied she's slower than the others. I separated her but she was less motivated to eat so they are all togetheragain, though I separate her to feed her the extra food. I didn't mention She's a Australorp which is usually a hardy breed.

Hi Sassy, She's pecking more this arvo, no meat today, offered her "porridge" softened ground seed, checked again for ticks mites worms and found nothing, still slow and particular in what she pecks at, motivated by the others, will buy yoghurt tomorrow as its too late tonite. Honey I have (guessing energy)but what's with the garlic? I know for people its good for colds how does it help chooks? Wondering if garlic paste will do or is fresh  or cooked better? Will try that too. Thanks I really don't want to loose her.

Powdered the chooks for mites today, Spike hanging in there, motivated by the others to eat and eldest son felt sorry for her and hand fed her for an hour today, that makes about 5 feeds in all today.  She has been wobbly on her feet for a couple of days now so surprised we still have her with us. Didn't try garlic but not sure if she's out of the woods yet, it's been a couple of weeks and she is still very weak.

Spike is still with us she must have a strong constitution, no more sickness just underweight and slow. Of a day she is separated and is hand fed. Us spending time with her has helped and Snitzel the bantam also kept her company today, which has motivated her to eat. Today she picked up her leg to scratch her head, unheard of a few days ago she had trouble moving. Looking hopeful.