Location - Florida Summer... so definitely humid. Old parquet flooring. (No idea how old but i would guess 50+ years.) Sanded down - spent a week sanding.(38 / 80 / 120) Stained with Varathane Classic ebony, 3 coats. Dried for weeks before we got a chance to clean and poly. (busy doing tile in the kitchen) Sat afternoon cleaned, vacumed, and very dry moped with water/vinegar. Sunday afternoon applied 1st coat of Varathane Oil based Satin Floor Finish - fast drying. Most of the floor is perfect. There are a few small places of discoloration, and one large area. In all these places our nearly black floor is now grey. It turned color fairly quickly. Pictures are the overall floor, then zoom in on the worst area. Thanks in advance your your help. Really frustrated / irked / confused / tired.