My ducks are a little over a week old, I noticed one of the ducklings hasn’t grown since he’s hatched. The others are 3x his size!  In the last 2 days I’ve noticed he’s stumbling and he’s breathing heavily with his mouth open. I sometimes here a clicking when he’s breathing. I’ve added probiotics to his water but I’m not sure if he’s drinking or eating at this point 
 I called my vet and they don’t deal with birds unfortunately. Any suggestions on what’s going on? Or what I can try to help this little guy
	
		
			
		
		
	
				
			
	