Replace Stealth Rock or Spikes on Skarmory with Roost. Skarmory needs Healing so that it has more chances to set hazards after a Defog, and Leftovers alone won't cut it. If you want, you could give Skarmory a Rocky Helmet as well, but that is more of a preference rather than necessity. :P
Replace Hurricane on Volcorona with Giga Drain or Psychic. If you choose Giga Drain, Give it Grassium Z; otherwise, give it a Focus Sash. :P