Similar Spells Drain Party Mana

My friend and I are playing two different characters (I'm a sorceress, he's a witch) but we are both doing an ice build. Frostbolt, IceWall, Cold Snap, and Comet are all draining his mana when I use the spells.

My spells are all level 16, his are all level 12.

He went Blood Magic and I went StormWeaver.

Even after reloading the part it still happens