<Update> young pullet can't walk and is lathargic NEED HELP Please

[fried green eggs]

Sick 3 month old pullet. She can't walk and is acting sleepy.
I noticed a few days ago that, one of the pullets I just bought a month ago wasn't out in the run with the others 3. She was asleep under the heat lamp in the coop but, looked fine so, left her alone.

The next day she wasn't out again so, I went in and found she can't walk and is really lethargic. Didn't try to get up or run from me so, I knew she was sick. I picked her up and offered her water and medicated chick feed out of my hand and she ate like she was starving but, would fall asleep every few minutes while eating. I checked her all over and she has no lice or mites and her vent and poop looks totally fine. I started feeding her scrambled eggs with probiotics and vitamins with electrolytes a couple days ago. I have also been hand feeding water and medicated chick feed so, she now seems aleart but still can't stand or walk. They have been on medicated feed since I got them.

I wormed her and the other 3 she is in with, yesterday morning. (Safeguard - pea size amount on tongue) Today my other pullet in this pen is now acting lethargic but, can still walk fine.
These chicks had been vaccinated for Mereck.
Any ideas ? What else can I do?

 

[fried green eggs]

I just went out to coop with one gallon of water with corrid in it. I found the pullet that acted lethargic this morning - dead.

The one that I have been feeding scrambled egg to hasn't changed - still can't walk but, she is now trying to stand. I gave her and the one rooster a few ml of treated water, other yourng roo drank out of bucket. Hope I don't loose anymore.

 

[Nutcase]

Did she get diarrhea at any stage ?

 

[fried green eggs]

All of them have had normal poop so, I wasn't thinking cocci. However today my two roosters in the pen had mustard colored runny poop. They still are very active and eating and drinking well. The hen is still eating well and acting like she feels a little better but, she still can't walk. All of her poop is mustard color so that means this is a virus???

 

[Nutcase]

The mustard colour could quite possibly be cecal faeces but you never know.

 

[fried green eggs]

She still can't walk but, is tring to stand but, her one foot is curled. She and the two roosters with her get a mix of yogurt,egg,dried milk,vitamins with electrolytes mixed with medicated feed and a little corrid water - two times a day. They seem very healthy other than she still can't walk. Should I make a cardboard boot for her foot? Would this help her start walking again?