PlantUML connect line style

I use plantuml to draw class diagram, but connect line position are not my expect(there are huddled together), the code as follow:

@startuml "mediator module"
' 默认线是圆弧状
' 多段线
' skinparam linetype polyline
' ortho 是垂直线
skinparam linetype ortho

class Mediator {
    +{abstract} createCtrl() : void
    +{abstract} ctrlChanged(CtrlParent*) : void
}

class ConcrMediator {
    +virtual createCtrl() : void
    +virtual ctrlChanged(CtrlParent*) : void
}

class CtrlParent {
    #m_pmediator : Mediator
    +virtual Changed() : void
    +{abstract} Enable(bool) : void
}

together {
    class Button {
    +virtual Enable(bool) : void
    }

    class RadioBtn {
        +Selected(bool) : void
        +virtual Enable(bool) : void
    }

    class EditCtrl {
        +virtual Enable(bool) : void
        +isContentEmpty : bool
    }

}

Mediator <|---down ConcrMediator

CtrlParent <|---right Button
CtrlParent <|---down RadioBtn
CtrlParent <|---down EditCtrl

CtrlParent o-left-> Mediator


ConcrMediator o-> RadioBtn
note on link : mp_rbtn1、mp_rbtn2

ConcrMediator o-right-> EditCtrl
note on link : mp_edtctrl1, mp_edtctrl2

ConcrMediator o-> Button
note on link : mp_login、mp_logout

@enduml

and draw result：

I`ve try to switch line style ortho/polyline and default, add toghter (Button, RadioBtn, EditCtrl), but not work, my expecting ConcrMediator connect lines hava some gap, just like:

When the subclasses of CtrlParent are at the same (vertical) level, it's very messy (especially with the note on link). So, I staggered the vertical distance of those subclasses (it's not exactly what you want, but I hope it's better):

@startuml "mediator module"
' 默认线是圆弧状
' 多段线
' skinparam linetype polyline
' ortho 是垂直线
skinparam linetype ortho 
skinparam nodesep 150

together {
    class CtrlParent {
        #m_pmediator : Mediator
        +virtual Changed() : void
        +{abstract} Enable(bool) : void
    }

    class Button {
        +virtual Enable(bool) : void
    }

    class RadioBtn {
        +Selected(bool) : void
        +virtual Enable(bool) : void
    }

    class EditCtrl {
        +virtual Enable(bool) : void
        +isContentEmpty : bool
    }

}

class Mediator {
    +{abstract} createCtrl() : void
    +{abstract} ctrlChanged(CtrlParent*) : void
}

class ConcrMediator {
    +virtual createCtrl() : void
    +virtual ctrlChanged(CtrlParent*) : void
}


Mediator <|-- ConcrMediator

' vary the vertical distance by making line longer
CtrlParent <|---- Button
CtrlParent <|--- EditCtrl
CtrlParent <|-- RadioBtn

CtrlParent o-l-> Mediator

ConcrMediator o-> RadioBtn 
note on link: mp_rbtn, mp_rbtn2

ConcrMediator o-r-> EditCtrl
note on link: mp_edtctrl1, mp_edtctrl2

ConcrMediator o-> Button 
note on link: mp_login, mp_logout

@enduml