We refinished the oak floor in our apartment this summer. We removed a wall, and had to put new floor on half of the room to cover the gap, and refinished the other half. The contractor did a good job and the finished floor matched perfectly. After 6 months though, some of the old planks that were refinished seem to be darkening around its edges. See images here: http://bit.ly/2krB1b6
Is this normal or did they do something wrong and this shouldn't be happening? Will this worsen over time? Is there anything I can do to fix it myself?
I'd like to get some advice before reaching out to the contractor. Really appreciate your help.