the white stuff could be "white fly". # V U# j& X8 V, t% U$ FI 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.- d% f- h9 R0 v7 a! w+ N" H2 D
Hibiscus is a typical plant, show helps a lot.