Separate her from your flock, preferably where they can still see each other but not touch. This could be a sour crop or a respiratory issue. When you had her mouth open, did you smell her breath, is it a neutral odor or does it smell fermented? How does her breathing sound when she's not being held? Is she rattling, does it sound labored, is she gasping? Is she sneezing, coughing or shaking her head? Are her eyes bubbly? Is she twisting her neck? Does she also have mucus discharge from her nostrils? How does her poop look? How does her tush look, clean, dirty, swollen or puffy, red. How about her vent? Pictures would be great as it helps to narrow down problems.She's got some sort of mucus on roof her mouth and only wants hide in the box