Former world No.1 Ko had made a solid start to the season, recording 19th, 31st and 10th in her first three appearances.
Now ranked 12th in the world, she sat 25th on the Tour's season points ratings before this week.
Meanwhile, Lee's difficulties on the PGA Tour continued as he shot a four-over 76 at the Arnold Palmer Invitational in Orlando, Florida.
Sharing 104th place, he faces a struggle to make the cut, let alone reel in a star-studded leading pack headed by 64 from Swede Henrik Stenson.
Lee has made the cut just once in his last eight tournaments, resulting in his world ranking plunging outside the top 150.
-NZN