Arcanist Iskandra's Elemental Exchange Question

Hey, I’m thinking about creating a Warlock or Druid build that focuses on a pet summon + crowd control (Devastation maybe?). I see that Manifestation (Iskandra’s Elemental Exchange) boosts pet elemental damage up to 120% and converts up to 30% of physical damage to elemental. This sounds great but it also decreases your personal elemental damage (when maxed) down to -40%. Ultimately, my question is does that -40% apply only to damage from your weapon or is that ALL elemental damage (so for example the Devastation skill) from all skills? I know might seem like a dumb question but it can make a big difference in how my build works.

Thanks in advance for any info.