I know I am so sorry .Thanks. I'm so upset about this.
The one walking backward may also have a different issue
Wry Neck ? selenium and vitamin E... Deficiency
Other options
1 ) take them back ? chances are their flock already has it .(would others do this ? )
2 ) treat them with antibiotics
3) is there something in the quarantine that they are reacting to ?
Cedar ? Alfalfa ? Chemicals ?
4 ) Apple Cider with mother in their water will de-congest them
If you decide to cull ..the area they were in should be disinfected good