2nd Directional light

I'm trying to get my shader to take 2 lights into account when calculating the final output. I've got 2 passes and the second uses ForwardAdd but no 2nd light is being applied. Is there something wrong with my shader code that would cause this?

Here's the shader:

 Shader "Infinite Runner/Diffuse Curve Specular" 
 {
     Properties
     {
         _Color ("Color", Color) = (1.0, 1.0, 1.0, 1.0)
         _Shininess ("Shininess", Range(0,1)) = 0.5
         _MainTex("Main Texture", 2D) = "white"{}
     }
     SubShader
     {
         Pass
         {
             Tags { "LightMode" = "ForwardBase"  }
             CGPROGRAM
             
             #pragma vertex vert
             #pragma fragment frag
             #include "DiffuseSpecularCurved.cginc"            
             ENDCG
         }
 
         Pass
         {
             Tags { "LightMode" = "ForwardAdd"  }
             Blend One One
             CGPROGRAM
             
             #pragma vertex vert
             #pragma fragment frag
             #include "DiffuseSpecularCurved.cginc"            
             ENDCG
         }
     } 
     FallBack "Diffuse"
 }

Here's the .cginc

 #if !defined(SpecIncluded)
 #define SpecIncluded
 
 #include "UnityPBSLighting.cginc"
                         
 uniform float4 _Color;
 uniform float _Shininess;
 uniform sampler2D _MainTex;
 uniform float _Curvature;
             
 struct fragmentInput
 {
     float4 pos : SV_POSITION;
     float4 posWorld : TEXCOORD0;
     float3 normalDir : TEXCOORD1;
     float2 uv : TEXCOORD3;
 };
                         
 fragmentInput vert(appdata_full v)
 {
     fragmentInput o;
     o.pos = UnityObjectToClipPos(v.vertex);
     o.uv = v.texcoord;
     o.posWorld = mul(unity_ObjectToWorld, v.vertex);
     o.normalDir = mul(float4(v.normal, 0.0), unity_WorldToObject).xyz;
 
                     // Apply the curve
     // Transform the vertex coordinates from model space into world space
  
     // Now adjust the coordinates to be relative to the camera position
     o.posWorld.xyz -= _WorldSpaceCameraPos.xyz;
     // Reduce the y coordinate (i.e. lower the "height") of each vertex based
     // on the square of the distance from the camera in the z axis, multiplied
     // by the chosen curvature factor
     //_Curvature=0.001;(
     o.posWorld = float4( 0.0f, ((o.posWorld.z * o.posWorld.z) + (o.posWorld.x * o.posWorld.x)) * - _Curvature, 0.0f, 0.0f );
  
     // Now apply the offset back to the vertices in model space
     o.posWorld += mul(unity_WorldToObject, o.posWorld);
 
     return o;
 }
             
 float4 frag(fragmentInput i) : SV_TARGET
 {
     i.normalDir = normalize(i.normalDir);
     float4 diffuse = tex2D(_MainTex, i.uv);
     float3 viewDirection = normalize(_WorldSpaceCameraPos.xyz - i.posWorld.xyz);
     float3 lightDirection = _WorldSpaceLightPos0;
     diffuse *= dot(lightDirection, i.normalDir);
     float3 specularReflection = normalize(lightDirection + viewDirection);
     float4 lc = _LightColor0;
     float specular = pow(DotClamped( specularReflection, i.normalDir), _Shininess * 150);
     return diffuse * lc + specular;
 }
 
 #endif