What happened to Rapid Spin on Forretress? It's one of the niches it has over Ferrothorn along with Toxic Spikes. If you're not going to Spin then use Ferrothorn which has arguably more auspicious typing and better resistances.
ScarfChomp wouldn't function without Outrage and Stone Edge. A Fire attack is for the most part useless since you'll be locked into something pitifully weak. Stone Edge lets it kill Volcarona and not get locked in while revenging DD Gyarados. Outrage lets you sweep lategame when you need that extra kick.
I'd replace either Metagross or Yanmega (maybe both?) for something. Since Skarmory walls you to hell and back. And it'd be mighty annoying if it Spike stacks and sits back on Jellicent to prevent spinning. Anyway, the best way to prevent this is to invest in 88speed Evs on Jellicent to outspeed other Jellicent and minimum speed Skarmory. As for replacements, you need something that can bust through common defensive cores like Ferrothorn/Jellicent/Gliscor, something like Mix Tyranitar can work since most of your team is immune to Sand damage and it helps activate Garchomps ability Sand Veil.
And use Bold on Jellicent