You should hold off with Electrolytes and discontinue Vitamins until you're done with just Corid in plain water. Like Wyorp was saying, no Vit B as Corid is a Vitamin B1 blocker and that's how it works to get rid of the Cocci who are dependent on B1 to thrive. Corid really does work in solving...
You're doing a great job! Everything sounds good. So let's hope the Corid treatment does the trick! You can add water to their starter to make a mash, they love that, but don't do ACV while on Corid.
Yes on the other chicks. When you start Corid it's good to do a "drench" with the sick chick and put it in water for all of the chicks. https://www.backyardchickens.com/threads/corid-oral-drench-instructions.1211991/ and like Wyorp said, make sure to not give anything other than chick starter...
:welcome Glad you joined and congrats on the chicks!! How old are they? More info. will REALLY help and a pic of your brooder set up and chick would be excellent. I'm going to say "maybe." It's normal at first when/if they're exhausted from shipping. But if suddenly she is lethargic and looking...