My six day old Light Brahma is exhibiting lethargy, loss of appetite, and is very wobbly. The other four chicks are doing fine. Yesterday the Light Brahma was very wobbly and seemed to favor one leg. She was lethargic, wouldn't eat, wouldn't drink. I ran to the local Tractor Supply and picked up some Corid and Nutri-Drench. Upon returning home, I found her on her back with her legs up and stuck between the brooder and wall. I immediately mixed the Corid and gave her some via eye dropper. Then I gave the rest of the flock the Corid solution. Then I boiled an egg, mashed it, and added some chick starter feed. She ate a little bit of it and then I gave a single drop of Nutri-Drench. After that, she seemed a little better, getting up and walking around [once or twice that I've seen], but still favoring one leg. She slept under the brooder all day except for the times I would give her Corid solution and fed her some mashed egg/feed. She seems to be doing better, but still very lethargic and making a puffing sound from her beak. On a good note, I did spot her out of the brooder to grab a drink and a bite to eat twice. She has the marek's vaccine and I've been feeding Purina NON-Medicated Chick Starter. All the chicks have been getting Sav-A-Chick electrolytes and probiotics since day one [07/22/13]. Electrolytes and probiotcs ended yesterday as they are getting the Corid solution. Her poop has been semi-solid/liquidy in a dark brownish red color. Today, she seems like how she was early yesterday. All the same symptoms seem to be coming back. She is definitely favoring her right leg and I could find nothing wrong on close inspection. When I flip her on her back, the weak leg trembles. When she sits, she sits on her good leg and sticks the weak one out. The other chicks still seem normal. Her poop is still semi-solid/liquidy in a dark brownish red color. Her crop was full last night, but nothing this morning and she was not interested in eating. Am I right in thinking this may be Cocci? Should I take another course of action?