Really sad day today. Went to bed and my little chick was eating and drinking. She was still slow to walk and often taking breaks to sleep under the brooder but at least every hour, I saw that she was actively pecking around. When I woke up this morning (2 days and 16 hours after initial treatment), I found her all alone, eyes closed, huddled under the ecoglow brooder while the other chicks were flying and running around their pen. She was making these very sad little peeps like she was in pain/calling for her mom, I am not sure. I moved her over to the water and after a few minutes, she reached her neck out and took a couple little drinks. Then she tried hard to walk back to the brooder but shook as she tried to pick up her leg and couldn't get more than one step without taking a break to sleep. I tried to get her to drink or eat something more but she didn't want anything. One of the other chicks zoomed past her at one point during this and she fell on her side and just laid there. I had a really bad feeling at that point and figured that she should at least get to pass in comfort and placed her back underneath the brooder. I propped her up with some pine shavings so she was in a little nest and walked away :C... She passed sometime in the next 30minutes.
I just want to thank everyone again for giving me so many suggestions so that I could give her the best chance possible. This order of hatchery chicks has been a roller-coaster of heartbreak but, for the first time, I feel sure that I did everything I could thanks to the responses here. I have never experienced cocci before but I think since she was the first to show symptoms, and being a hatchery chick that already is weak, that she just didn't have it in her to survive this. I know now not to trust the cocci vaccine to protect them! I will just feed medicated feed instead and be careful to look for and treat the symptoms immediately. The only thing that confuses me is why she seemed to get better yesterday and then get worse overnight but at least her suffering is over.
Oh no. So sorry!
She might have succumbed to a secondary infection, since her digestive tract was so damaged. That might be why she was doing better the day before, but still didn't make it. I believe e.coli is the main culprit there and it can kill quickly.
You did all you could.