Through carelessness, plants were left standing on the maple floor and left black stains due to water. I have read some info on the web about sanding and then bleaching. I had some wood bleach but after two attempts, you can see that I have had little success. I have used a coarser sandpaper so as not to close the tight grain. What I used was Liberon Wood Bleacher. The darker areas in the picture are wet and the light areas are dry. The wood seems to bleach but the stains remain. The bleach was purchased over a year ago and used for something else. Could it be weak? What product has been successful for anyone?

Any advice would be appreciated.
Carol