We bought couple day old "East Indies Black Ducklings" and now in not sure if that is what we have..

I’m unfamiliar with what a spring balance is. Since they are a little bit older can you take another picture with some sort of size reference in the picture to refer to?

 

How old are they again?

 

Mine? Mine are almost a year so fully grown. One of my girls is about the same size as him, the other two are smaller

 

They are beautiful, I love the purple and blue, but I am sure I've read that's an instant disqualification for showing black east indies

Not sure I've ever met a khaki, but I have a feeling they could still be cayugas if they are larger than them. @CayugaJana will be able to judge better.

Either way, I'm glad you got a full refund....

 

Maybe the description in this post will help.

https://www.backyardchickens.com/threads/cayugas-or-black-east-indies.1132395/#post-17658068