He's a cutie
The breathing is concerning, Infectious Bronchitis and Mycoplasma are a couple of common respiratory illnesses. Usually these are accompanied by more symptoms. Milder cases of Infectious Bronchitis may just present with sneezing.
Tylan50 can help with secondary infections (bacterial) , but it not that effective if treating Infectious Bronchitis (viral). You can try treating him to see if there is any improvement. Tylan 50 can be given orally 2X per day - dosage is .20ml per 1lb of weight. You want to make sure he has plenty of ventilation, is eating/drinking well and that his crop is emptying overnight.
You can also use the VetRx in addition to antibiotics, since it's an "natural remedy".
Just to cover all bases - what type of food/treats do you feed him, does he have poultry grit available free choice and have you checked for any signs of lice/mites.