I am wondering how old these calves are.  The rumen in a calf is not fully developed until a couple of weeks after birth.  I am wondering if he is feeding all forage too early.  The fact that he fed sugar and they improved makes me wonder if they are short on energy.  I found a couple of articles that I found interesting. 

Calf rearing

Calf Digestive System

Is this the first time he has been raising calves? or has he raised calves in the past?