It's common to slow down egg laying, lose weight, and have a lower food intake with MG. After you Tylan 50 is finished it would be helpful to give them some probiotics such as Probios Dispersible Powder 1 tsp per gallon of water for a few days. It is also good to use once or twice a week just...
It could be a respiratory disease such as mycoplasma (MG) or possibly coryza. Coryza may have a bad odor. Antibiotics such as Tylan and tetracycline may be used to treat symptoms, but these diseases are chronic and may make carriers of the flock. Coryza is better treated with Sulfadimethoxine...