Chickens can have all kind of innate issues. They sometimes suffer from an innate deformity as for instance of the oesophagus/trachea or a heart condition which makes them gasp for breath and having trouble eating. And deformities of the digestive tract are often found in rumpless breeds.
So, don't beat yourself up if he does not make it. Sometimes there is nothing one can do to better these conditions.
So, don't beat yourself up if he does not make it. Sometimes there is nothing one can do to better these conditions.