HI everyone -- hoping all the smart folks here can help me diagnose this problem. I recenlty bought a 40 year old house which has hardwood only in the living room. I don't think the floor is original, but its definitely not new and has been installed for a number of years. I can't figure out how this floor is finished, but it is incredibly sensitive to water. Even a quick wipe with a damp cloth removes the finish and leaves a whitened and dull mark. If water is actually spilled, forget it. Every little drip or attempt to wipe something up leaves a permanent dull spot. I've lived with hardwood floors in all my homes and have never seen anything like it. I'd think the floor was completely unfinished except for the fact that it does have a sheen to it that natural wood does not. Somehow its actually more sensitive to water than raw wood. I also cannot for the life of me figure out how the prevoius owners kept the floor in such good shape, because there were no dull spots or water marks except for the ones i caused! Any help figuring out how this is finished and how i can re-seal (other than taking out all the furniture, sanding, and putting on a few layers of poly) would be greatly appreciated. I'm just stumped at how the previous owners kept it looking good and its suddenly so sensitive. The first pic is a little hard to make out, but you can see a dull circle where i literaly wiped up some dirt wtih a dampened cloth and then wiped dry. The other two show water stains.

I levelled the floors in two halves months apart. As it turns out I got to a final section right above the foundation where there is this kind of opening for vents. It looks like a wood window frame. I think it used to be the crawl space vents but then it was blocked up with plywood and used as a vent for the bathroom and dryer. This thick wood window is actually about 1" higher than the level I need to level the entire subfloor at so I need to reduce it somehow. What would be best - a planer, sander? something else? I doubt I can cut the whole thing out since it looks like it provides some structurak support to the wood square wall above.