I've just checked all my bags with a twist lock. I have this tarnished look on my printed ledbury, choc ant, black ant and oak ant (before i sold it, although it came like this) All these are older bags but printed ledbury has only been used a handful of times.
I* wonder why this happens then, will they are eventually tarnish or is it just a handful?
I would send it back, don't worry the lock can be easily changed so you'll get ink Alexa back x