I have checked her crop at night when they roost and first thing in the morning inf a couple of times. There isn’t much in it at bedtime and it is flat in the morning.
When I take out bread, scratch, etc she will run after it but rarely seems to get much if she is with the other girls. When I had just her in the run night before last and took some tortilla chips she pecked at those and hate a little bit. But I had trouble getting her to eat the mash yesterday.
		
		
	 
Do you know if she goes in a nest and spends time there without laying, or if she doesn't go at all ?
Have you checked she is not laying somewhere different , and also check for signs of abnormal eggs that could be anywhere around the coop (hens that lay soft shells tend to do it like they poop, just wherever they are.)
Any chance that she could be really moulting and not just a little ? I seem to remember they are too young for that, but not sure? If they start in the neck or head, it doesn't show at first, you’d have to check beneath if you see pin feathers. Molting will cause a break in laying. It makes some hens reject commercial feed, and go cranky. The symptoms fit pretty well what you describe.
Other things to check for : lice and mites ; feeling her abdomen in case it feels swollen and either abnormally hard or squishy.
	
		
	
	
		
		
			Gorgeous photos as always.  So glad you found the lamb and got it back to them.  Praying it recovers.
		
		
	 
I forgot to give some news, my partner saw the couple of shepherds and they said the baby lamb was doing great ! It just needed a few bibs to go running around ! I’m so happy. I’ve had so many times to give bad news to animal owners when I find them dead or dying in the mountains that it's nice to know this one made it.
Friday tax. It's more a landscape picture than a butt photo but at least it preserves molting and dirty chicken's dignity ! 
Gaston, Cannelle, Lily and either Nieva or Alba enjoying the wet grass.