Decks, Patios, Porches and Docks - White spots on new mahogany porch floor

Hi. I'm having trouble with my new porch floor. I sanded it and cleaned it with turpentine and then applied a coat of oil-based spar urethane...As it dried, white spots appeared that were not there before. A lot of the floor is fine but about 30 percent has areas ranging from a transparent-looking whitish film over several inches of plank to little white dots that look like paint.
Is this mildew? The floor did sit unprotected for a while before I finally got to protecting it. (It's a covered porch).

I've done a lot of oak and pine floors and we never used turpentine after sanding. What was the reason for that? What type of sander did you use and what paper?

I assume the turpentine was used to remove any sanding dust [mineral spirits would have been cheaper] What kind of rag was used? Was it clean to start with? Did you fold or change the rags frequently to prevent redistribution of what was cleaned off the flooring?

Will the spots sand off? Is this porch enclosed? Spar Urathane while better than regular poly doesn't weather real well.

When you sand floors, you vacuum to remove the dust. There was no reason to use any chemical at all. Resand and restain the affected areas.