Is there anything unusual in the coop such as the bedding, the ventilation, wet conditions that could have been moldy, or anything else you can think of? Where did you get her? Chicks that have come from a place where there could have been a bird carrying a respiratory disease, such as MG, can show symptoms around 3-4 weeks old. MG can also be passed through the egg. Antibiotics such as Tylan 50 injectable given orally 1/4 ml once or twice daily for 5 days may help treat symptoms of a respiratory disease. Oxytetracyxline, Gallimycin, Lincomycin/Spectinomycin 50, and Tylan Soluble Powder can be used in the water instead if she is drinking well.