Sorry for such a long question.If ynu don't get what I mean here's an example.
A team of Swampert,Charizard and Torterra are going through a dungeon.
And a Graveler used Explosion(or was it Selfdestruct.) Swampert's max HP was halved.Torterra's max HP was halved
But Charizard's max HP was cut down by 1/3.Is there a reason why fire type Pokemon get less damage from explosion and selfdestruct?