I believe my duck is dying.

[Csquare]

So I had gotten three ducks, they grew got almost feathered. I got another duck and the three older ones didnt like him so he stayed in my room. We waited a while and got him a friend, but his little duck friend died over night. SO now for the main concern the morning I found the little duck dead my older one seems sick.
His symptoms include:
Stumbling
Constant blinking
Decreased appetite
Thirsty
Stomps his feet if he does walk
Nasal discharge
Lethargy
Please help me, it was hard losing the first little guy.