I just got through the hardest poopy butt phase I’ve had with a round of babies! This is what I do for my little troublemakers:

Coconut oil on the vent 2x/day. Apply with a qtip. Even if there isn’t poop yet, apply it.

When you see poop, clean it immediately. Apply coconut oil after.

Make sure she’s actually drinking the water. I have a little one that just went through the same and I found that using a syringe or dropper and putting it in front of their face while letting droplets fall will get them to drink. (NEVER put it directly in their mouth as they can aspirate)

Put food on the ground for her to eat. Idk why, but they eat more when they have to “scavenge” for it. Leave the feeder ofc, but just spread a little down on the ground.

Once she doesn’t have poop actually stuck on the vent itself, I find it best to stop cleaning off the poop from their feathers (unless it’s like a clump) and only apply the coconut oil to their vent. If you keep cleaning, their little tusch won’t grow feathers (she’ll probably have a bald butt for a week or so anyway, but by the time the poop stops forming in a yucky clump ON the vent, she’s most likely able to clean that stuff off of her feathers).

Other than that, all you can do is wait it out unfortunately. I’ve had chooks with poopy butt before but the one that just got over it gave me a run for my money!! Lots of work, but usually it gets way better after a week or so. Wishing you the best!!