the white stuff could be "white fly". ( G$ h1 p% n5 _. t1 z; C3 gI had the same problem before. It because your plant is too wet. I showed the leaves twice a day for a whole week, then the white filies were all gone.9 U$ r% }% j& o" m7 K6 D, p. V6 Y
Hibiscus is a typical plant, show helps a lot.