If you can take close up photos of the suspect area of rust it would be more easily seen on a computer monitor. I can't tell from the photos posted. Clean the metal surface with metal polish, q-tip and a paper towel.
That will get the surface stuff. Not any pitting or all discoloration. Keep that one isolated from your others and check on the progress or the lack of it. I've had a few I quarantined and they ended up not having the rot. I've had a couple that did have it.