Aquariums: What do I have here?

Alrighty, so here are my green spotted puffers, or so I believe, the ones with the white belly, definitely GSP, the question is the one with the spotted belly. Do I just have a weird little dude or a completely different type of puffer?

I know the green spotteds will get dark when either sleeping, just waking up, sick, stressed, etc.. when awake they should be light bellied. Water parameters are rock solid and originally I just thought the little guy might just be sick or something… that was a bit over a year ago when I got them, nothing has changed, has no problem eating or moving around just like the others, he’s just got a spotted belly and looks a little different in a few different places. What is really weird is his belly is bright white aside from the black spots.

Also yes they’re being transitioned to full marine, very slowly but we’re a bit over half way to full salt. All the puffers have been completely fine with the transition, including the guy with the spotted belly.