My 6 month old Barred rock bantam cochin rooster is sick and i have no idea whats wrong. Hes been acting very lethargic, and has a very bad sneeze/cough. He acts very tired and moseys around the pen, not looking very alert. Hes normally very chatty and active, but hes still talking a little bit. It actually sounds to me like hes crying
He is drinking and eating and ive been putting Terramyacin in his water daily. Hes still with the hens but none of them are showing signs of being sick. Theres no discharge from the eyes or nose but he is starting to lose a lot of his feathers. Being as hes too young to molt its scaring me a bit, though the weather has shot up into the upper 80's for the past week which i suppose could have thrown him into a molt.
He is my favorite bird and i would be heartbroken if anything happened to him. Any ideas or suggestions??

He is my favorite bird and i would be heartbroken if anything happened to him. Any ideas or suggestions??