So the vet confirmed my suspicion that there's coccidiosis, but he also said there are uric acid crystals in the fecal that can be caused by high-protein feed.
The pullets are in a transition from flock raiser feed (20% protein) to layer feed (~16%) protein with scratch grains mixed in so the mix right now is about 25% grower, 25% scratch and 50% layer. Nothing terribly high in protein... they have a run and get the occasional handful of mealworms, but nothing excessive.
The vet said it could be bird-specific (I'm thinking maybe breed-specific as this pullet is also an Orpington) but the outlook doesn't seem great.
She's willing to let me syringe water/mush into her beak and eats some on her own. At this point, it seems to be a waiting game if she'll recover as she seems pretty lethargic at the moment.
You are not feeding high protein food. 16-20% protein is normal, but your scratch grains is only 7%. I would skip the scratch, and continue the flock raiser until they are laying. I think that urates (uric acid) is increased with dehydration. So maybe increasing her fluid intake would help. Are you giving more Corid now, since they still have coccidiosis? Or did the vet prescribe something else?
I have them on Corid (2tsp/gallon - this is day 3, I'll treat for 5-6) and have been syringing water to the lethargic hen 3+ times a day on top of what she will drink on her own.
I wormed the flock with Safeguard as a precaution about 2 weeks ago so they will get their second dosage starting this weekend.
Well, she made it through the weekend but passed today. I don't think they got enough fluids/food to fight the infections because I'm not comfortable enough to try tube feeding. And I've noticed a fair few of my flock avoid the Corid water.
So, everyone is getting Corid syringe treatment with applesauce mixed in to make it palatable. So far that's been rather effective. The Corid water is still out, but at least I know they're getting a fair dosage each day.
I have one other Wyandotte that seems a little thin but has a strong appetite (she's loving the applesauce and is easy to medicate) so fingers crossed this will be my last bout of coccidia with these pullets.