Honestly, I would replace them all. Brand new o-rings can be bad, even when they visually look fine. You have no idea how long an o-ring has sat on a shelf in a warehouse or store before it made it into your hands. Over time o-rings degrade on their own. That "new" o-ring could have been sitting around, un-lubed for a year before you received it. No way to know.
Usually, when I have a leak that I'm having difficulty diagnosing, if replacing one or two o-rings still leaves me with a leak that I can't locate, I simply replace them all. It's very rare when that doesn't fix the issue.