And are there any other things I can do other than start over?

In the bright light it's this light

I'm not expert, but I think if you haven't sealed them yet, you can try the final coat darker. I actually really like that color. Would it go with your decor? I could see this being gorgeous with a light, airy look. And you're talking about painting the bannister black, right?

Did the final sample have a "finish" applied? If so the "slightly darker" could be coming from a solvent based finish that ADDS "darkness" because it turns amber/orange once applied.

You might want to add a single coat of finish and watch that patch turn "darker". If you need to start over, the cost of a sand+refinish = $3-$5/sf.

Thank you both for your comments! I have such a pit in my stomach because it looks "pink" in spots. I wanted the light and airy look but now I'm second guessing everything! I basically want it a tiny notch richer - the pictures are with one coat of poly. I'm wondering if when they put the final poly finish if they can add a touch of warmth to darken/richen it or is it too late since there's on coat of poly already on it?