9 week old pullet won’t stand up

[Lp21]

I have a 9-10 week old lavender Orpington pullet who is decking. We treated all the chickens and the coop for lice/mites two weeks ago with elector psp, and we are now mite/lice free (I think we had lice but not positive). 4 days ago I noticed my lavender was lethargic but she continued to eat and drink. Yesterday she wouldn’t stand so I put her in a playpen w shavings and added electrolytes to her water. She will eat and drink if I feed her by hand and she can stand and walk but seems so weak and would rather just lay there. She is very skinny. She has been on medicated feed since she was a baby. I was planning on switching once our bag runs out this week. She doesn’t have any respiratory issues. She does seem like she’s almost straining to poop. Her vent keeps pushing out but not to the point of a prolapse, just like she’s pushing. She has had some diarrhea. Could she have coccidia if she’s been on medicated feed this entire time? None of the others are acting like this. Her comb also got darker but I think that’s just her coloring. Her wattles seem to be pale now. Thoughts?
Last pic was from a week ago and the others are recent.

 

[BlindLemonChicken]

What does her poop look like?

 

[The-White-Elephant]

Perhaps it might have injures her leg somehow? Maybe sprained it or broken it?

 

[Lp21]

What does her poop look like?

She has bad diarrhea and it seems like she’s still pushing out her vent a lot. I’m going to treat a corrid. Wouldn't others have coccidia as well though? She’s the only one w diarrhea or any of these symptoms. And she is eating drinking but still won’t walk much.

 

[BlindLemonChicken]

The medicated feed should have helped but if she has another issue cocci can exacerbate it. At least that's been my experience. Do you have nutridrench? I don't have much advice but I would try the nutridrench if you have been using medicated feed.