Event modding: How to target specifically only heir or only ruler

I've come across a problem with events when I want to change a trait for the ruler or the heir specifically.

country_event = {
    id = disease.107
    title = "disease.100.name"
    desc = "disease.107.desc"
    picture = GFX_evt_genetic_modification
    
    mean_time_to_happen = { months = 1 }
    
    trigger = {
        OR = {
            any_owned_leader = {
                has_trait = leader_trait_disease_stage1 
                leader_class = ruler
            }
        }
    }
    
    immediate = {
        random_owned_leader = {
            limit = {
                has_trait = leader_trait_disease_stage1
                leader_class = ruler
            }
            add_trait = leader_trait_disease_stage2
            remove_trait = leader_trait_disease_stage1
        }
    }
    
    option = {
        name = UNFORTUNATE
    }
}

This code targets both the ruler and the heir, yet I would like to do them separately, if it's even possible.