Does anyone know what might be wrong with this sunflower or is this just part of the stem? My other 2 don't have these black dots though.

It might be a fungus that can commonly affect sunflowers. I suggest you google "sunflowers with black stems" I was interested in your picture and found quite a bit of info when I searched. Perhaps someone with more knowledge will also be along to give you some advice. Good luck!

Seems to be more of a genetic trait than any disease. Do you know what cultivar it is?

I agree with Arico.
I've grown sunflowers many times and some had this, others didn't. It doesn't appear to be anything "harmful".

Thank you guys so much. This is my first time growing sunflowers. I do not know the exact cultivar as these are from a mix seed packet.