So glad to see everyone is doing better and that sick chick is hanging in there!
There are lots of opions on medicated vs non medicated starter here...personally I use a bag of medicated and then switch them to non medicated.
and I don't offer grit until they start eating treats after a...
Some questions...
What temp is your brooder? (If too hot they will stay away from heat source, too cold they will huddle together under heat source-either can cause lethargy.
What are you feeding them?
Have you tried adding electrolytes? Like sav-a-chik?
What is the bedding? I ask this...