In base it petrifies everyone but the victim. If a renaud is petrified they can act as a barrier creating a cone of safety. The further back from the Rennaud you stand, the narrower the cone. If closer, then the cone is wider. However if you are standing inside the renaud's hitbox (i.e. The red circle on the ground when targeted) then they don't act as barriers and the petrify still hits everyone, which is what it sounds like is happening to you. Make sure the victim is standing further away from the renauds and that everyone else bunches up onto the invisible cone if safety