One of two things sugar bloom or fat bloom.
What is sugar bloom?
A condition affecting the surface of chocolate. The chocolate adopts a dull, tannish-white color and feels gritty when touched. Only appearance is affected - not taste. It is caused by condensation of water vapor from air on the chocolate surface. The sugar in the chocolate dissolves in the water, then the water evaporates and the sugar crystals remain on the chocolate.
What is fat bloom?
A condition affecting the surface of chocolate. The appearance is similar to sugar bloom (dull, white), except it is shiny and feels greasy when touched. Taste is unaffected. It is caused by the migration of cocoa butter crystals to the surface and subsequent recrystallization. The "migration" is hastened by warm temperatures and prolonged storage.