Solid Hardwood, Engineered and Laminate Flooring - Bedroom transitions

I've got red oak floors that are from 1956. They sanded well except for the areas where the bedrooms meet the hallway. There used to be carpet throughout in this house and the transitions from the bedrooms to the hallway has black nail holes that I can't really lighten up to well with sanding. What options do I have to get rid of these spots? They run the length of the doorways.

Small black marks like this are usually from rust and oxidation of nails and will go the depth of the nail. Though it will get smaller as you sand down. One option is to punch holes in the black marks about an 1/8" deep and use wood filler the same color type as wood. This won't completely hide them but will make them less noticable. The only other option is to replace the boards.
AL

What about using bleach to lighten the blackening and then filling with wood filler?

I've never tried it on the black marks. You would have to do it with an artists paint brush and only get it on the black. Or you will end up with three different colors. Bleached black wood, bleached wood and natural wood. I doubt that it will give as much of a similar color to the natural wood by bleaching rather than denting the black and filling it. You can try it and inform us what your outcome is. You will still be able to punch down the bleached black marks and fill them. If not satisfactory.
AL

I'll post the outcome when I get there.