Glass shader turn white when double sided!? Am i misunderstanding somethig???

Can someone send help? There must be a very stupid issue cus i am a newb. I got this glass surface shader with a normal map when i tried to turn it double sided by adding Cull Off, the whole things turn white. it doesn't seem to be the problem of _Color.

 Shader "Custom/Glass" {
     Properties{
         _Color("Color", Color) = (0.5, 0.5, 0.5, 1)
         _MainTex("Albedo", 2D) = "white" {}
         _Smoothy("Smoothness", Range(0,1)) = 0.5
         _Shininess("Shininess", Range(0.01, 1)) = 0.078125
         _myAlpha("Over All Alpha", Range(0.0, 1.0)) = 0.5
         _NorTex("Normal", 2D) = "bump"{}
 
         //Rim
         [Toggle(RIM)] _RIM("Fresnel Rim?", Float) = 0
         _RimColor("Fresnel Rim Color", Color) = (0.49,0.94,0.64,1)
         _RimAmt("Fresnel Amount", Range(0,5)) = 1.5
     }
 
     Subshader
     {
         Tags {"Queue" = "transparent" "RenderType" = "Transparent"}
         LOD 100
         Cull Off
         ZWrite OFF
         
         Blend SrcAlpha OneMinusSrcAlpha
         CGPROGRAM
         #pragma surface surf StandardSpecular alpha:premul
         #pragma shader_feature RIM // rim fresnel toggle
         
         sampler2D _MainTex;
         sampler2D _NorTex;
         half4 _Color;
         half _Shininess;
         half _Smoothy;
         fixed _myAlpha;
 
         float4 _RimColor;
         half _RimAmt;
         
         struct Input
         {
             float2 uv_MainTex;
             float3 lightDir;
             float3 worldPos; // world position
             float3 viewDir; // view direction from camera
         };
 
         void surf(Input IN, inout SurfaceOutputStandardSpecular o)
         {
             
             float rim = 1 - saturate(dot(IN.viewDir, o.Normal)); // calculate fresnel rim
 
             #if RIM
                 o.Emission = _RimColor.rgb * pow(rim, _RimAmt); // fresnel rim
             #endif
             
 //Output
             fixed4 c = tex2D(_MainTex, IN.uv_MainTex)* _Color; 
             c = (c-0.5)*10 + 0.5;
             o.Albedo = c.rgb;
             o.Normal = UnpackNormal(tex2D(_NorTex, IN.uv_MainTex));
             o.Smoothness = _Smoothy;
             o.Specular = _Shininess;
             o.Alpha = _myAlpha;
         }
         ENDCG
     }
 
         FallBack "Transparent/VertexLit"
 
 }

@bgolus