Outline on Sprite Mask when switching from Discard to Alpha

I am using the following shaders to mask two sprites:

Shader "Sprites/Stencil Mask"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
    }
 
    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
 
        Cull Off
        Lighting Off
        ZWrite Off
        Fog { Mode Off }
        Blend SrcAlpha OneMinusSrcAlpha
 
        Pass
        {
            Stencil
            {
                Ref 1
                Comp always
                Pass replace
            }
     
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile DUMMY PIXELSNAP_ON
            #include "UnityCG.cginc"
     
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };
 
            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
            };
     
            fixed4 _Color;
 
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                #ifdef PIXELSNAP_ON
                OUT.vertex = UnityPixelSnap (OUT.vertex);
                #endif
 
                return OUT;
            }
 
            sampler2D _MainTex;
 
            fixed4 frag(v2f IN) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, IN.texcoord) * IN.color;
                if (c.a<0.1) discard;            //Most IMPORTANT working Code
                c.rgb *= c.a;
                return c;
            }
        ENDCG
        }
    }
}
 

Shader "Sprites/Stencil Draw In Mask"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
    }
 
    SubShader
    {
        Tags
        {
            "Queue"="Transparent+1"              //DON'T FORGET this must be drew later to catch Stencil Ref value.
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
 
        Cull Off
        Lighting Off
        ZWrite Off
        Fog { Mode Off }
        Blend One One
 
        Pass
        {
            Stencil
            {
                Ref 1
                Comp Equal
            }
 
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile DUMMY PIXELSNAP_ON
            #include "UnityCG.cginc"
     
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };
 
            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
            };
     
            fixed4 _Color;
 
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                #ifdef PIXELSNAP_ON
                OUT.vertex = UnityPixelSnap (OUT.vertex);
                #endif
 
                return OUT;
            }
 
            sampler2D _MainTex;
 
            fixed4 frag(v2f IN) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, IN.texcoord) * IN.color;
                c.rgb *= c.a;
                return c;
            }
        ENDCG
        }
    }
}

This worked fine on my iPhone 6S but not on older devices like my iPhone 5 running iOS 7. I read that this was because of the Discard statement and that I should instead set the alpha to zero.
I did this, but then I get an outline around my object. I have tried to disable anti aliasing to troubleshoot, but that did not work.
My new shader (only changed that one line from discard to c.a = 0)

Shader "Sprites/Stencil Mask"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
    }
 
    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
 
        Cull Off
        Lighting Off
        ZWrite Off
        Fog { Mode Off }
        Blend SrcAlpha OneMinusSrcAlpha
 
        Pass
        {
            Stencil
            {
                Ref 1
                Comp always
                Pass replace
            }
     
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile DUMMY PIXELSNAP_ON
            #include "UnityCG.cginc"
     
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };
 
            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                half2 texcoord  : TEXCOORD0;
            };
     
            fixed4 _Color;
 
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                #ifdef PIXELSNAP_ON
                OUT.vertex = UnityPixelSnap (OUT.vertex);
                #endif
 
                return OUT;
            }
 
            sampler2D _MainTex;
 
            fixed4 frag(v2f IN) : SV_Target
            {
                fixed4 c = tex2D(_MainTex, IN.texcoord) * IN.color;
                if (c.a<0.1) c.a = 0;            //Most IMPORTANT working Code
                c.rgb *= c.a;
                return c;
            }
        ENDCG
        }
    }
}

results before (with discard):
89220-screen-shot-2017-03-03-at-81503-am.png

results after (with c.a=0):
89218-screen-shot-2017-03-03-at-81447-am.png

How can I get a clean sprite mask without using discard?
Thank you :slight_smile:

I dont know a lot about shaders. But maybe se c.a to null? If there even is a null value