Red Green wrote:

And oxalic acid is used for wood bleaching. Available at real paint
stores. It would need to be sanded anyway to get the finish off so the
acid can work. May end up being a bigger mess than what you already have.
Probably will since you call them tiles vs wood verbage. Definitely more
work than you plan.

I have had good luck using oxalic acid for removing water stains from finished
floors. The water got through the finish, the oxalic acid can too. If the
boards aren't warped, I'd keep the boards wet with oxalic acid until the stains
are gone and see what it looks like. Wet cloths for a couple of hours should do
it.

If the boards are warped, I'd sand that out first. Then I'd use oxalic acid to
get rid of the stains and refinish the area. It's not that hard, but can be
tricky if you haven't done it before.

-- Doug