We have a 4 month old, starlight green egger, who is acting lethargic. She will sit down and rest when none of the other birds are doing so. We've watched her closely last night and this morning and she is not eating. We tried 2 of their favorite foods (Chard and watermelon) and she comes up to it, gingerly pecks at it, but doesn't take any bites. She drank normally this morning. We've seen one of her poops and it was normal, but small. Her crop is flat/empty and was last night before bed as well. Her eyes, ears, and vent are all clear/clean/normal. We checked her beak/throat and that is clear. She is still moving around some and came into the coop last night on her own. We are in MN, and it has been hot and humid, 90s plus high humidity the last 3 days. We live in a neighborhood. We have 6 chickens total and they are contained in a large coop and run. Shade is ample as is water and food. We occasionally let the birds out to free range and we did this yesterday for about 30 minutes around 430pm. From what my daughter and I can remember, she was acting normal then and eating grass and what not. No new birds introduced lately. No new foods introduced. The birds free range 1-2x a week and are fed Dumor layer crumbles. We supplement with some type of fresh green every day (chard, spinach, etc). Any ideas on what could be going on? Anything we could try? Or just watch and observe right now? Thanks so much! Of course, this is our favorite chicken of the 6, Montana. Pics of Montana and coop/run attached.