Yes.  Beans in pic 018 and 019 look yellow to me.  In 018, the top looks more "yellowish" than closer to the camera. I don't know if that is just blurring, or if it is actually more yellow. 

I definitely think you should pull tissue samples.  If you see pockets of beans that look "more yellow", and pockets that look "more green" - pull 2 samples and label them accordingly.

Also, dig up some plants and see how well they are nodulated. 

How recent is the most recent soil test on this farm?  What are your soil K levels like?