Listless and not eating

[Hive_and_hens]

Hi All- new to the forum but value all opinions!
I have a, 4month old pullet (1 of 2) who I found today completely listless-standing in the one spot. Normally I have to chase them to pick up and they are very food orientated. She is lethargic not eating a thing (even meal worms)
There is no fight when I pick her up and she is almost motionless if left alone.
Her poo this morning was diarrhoea (See pic- don't mind the leaf in the centre) , I have recently wormed her an her sister 1 week ago with avitrol tabs but otherwise they have pretty consistent environment. Pullet feed, water with ACV, treats include live meal worms and saltanas.
There is not signs of respiratory distress, her vent appears clean/clear.
The coop has no evidence of bloody poos (concerns with coccidiosis) but I'm out of ideas. Her sister is looking normal at this point and they are inseparable so share all the same environment.
Any ideas?

 

[Smuvers Farm]

Age? Are they laying yet? Could she be egg bound?

 

[Hive_and_hens]

Hi
No she isn't laying yet. Poppet is a Salmon faverolle and she is about 4months old.
She has done 3 poos today all liquid- yellowish and white.
I'm not sure if I should worm her again or if it might be coccidiosis. All symptoms are common in so many conditions it's hard to pin point. She was fine yesterday but today totally abnormal lethargy.
Thanks