Looks like you have cottony scale on your hibiscus and this tiny sucking insect hides under the white fluff to feed on the plant. Get busy now removing any infected leaves and do not put into the compost. You can clean buds by dipping a cotton swab into rubbing alcohol and dabbing the cottony deposits to dry up the insect hiding inside. Keep your plant well watered as stressed out plants attract more insect and disease problems. If the scale comes back or the plant is too large for hand picking you can spray Neem or Horticultural oil on the plant following label instructions. You may need more than one application to control this persistent pest.  Keep growing, Marianne Binetti