Trainer King T. Leatherbury scratched Rogue's Pleasure before the running of yesterday's fourth race when he was informed by the racing stewards that a test on Flush N Diamonds, the winner of the ninth race Tuesday, had come back showing a possible positive indication for a prohibited substance.

J. Fred Colwill, the steward representing the state, said yesterday, "We called Leatherbury in when our lab came up with a possible positive. We split the sample and had it sent off to an out-of-state lab.

"Leatherbury said that he believed he was giving his horse vitamins and supplement. I understand that it is possible for some vitamins and proteins to show positive. In any case, we'll know in a few days. Meanwhile, we gave Leatherbury permission to scratch Rogue's Pleasure because he treated the horse with the same vitamins and supplements."

Flush N Diamonds was ridden by apprentice Alberto Delgado Tuesday and paid $11.40. He topped a 5-9-2 triple that paid $1,689.60. Rogue's Pleasure was the morning-line favorite for his scheduled race yesterday.

Contacted after his talk with the stewards before the running of the fourth, Leatherbury, who has won two national training titles, said, "Yes, I scratched Rogue's Pleasure with regret because she was in good form. But I did treat her with the same vitamin supplements that I treated Flush N Diamonds with. I felt it better to scratch her and find out what all this is about."

Maryland-breds Jameela, Lady Dean and Weber City Miss are among the leaders in voting for national and state champions in the 4-year-old filly or mare category. Lady Dean has won the most money this year ($310,273); Jameela has won the most prestigious races, the Molly Pitcher, Mahubah and Delaware handicaps, and Weber City Miss had the most impressive victory, the $200,000-added Beldame at Belmont.

Two-time jockey champion Dave Gall will ride today in Laurel's sixth race on Holiday Dancer. Gall, 41, led the nation's riders last year with 375 winners. In 1979 he won with 479 mounts. Gall has been riding in Illinois and West Virginia.