Elemental split creates 2 clones of you with the exact same effects on as you, both good and bad. If you have eldritch stones on before you make the clones they will still have it on. This means when your shield explodes their shield also explode and you take massive damage. And they seem to bounce of each other, so the first shield hurts the 2 other people whose shield absorb then explode to deal more damage, and then the third shield does insane damage.
Either way Eldritch stone shouldn't hurt allies.