Mesh (custom shader) appears in front of particles (default shader)?

So, I have a couple screenshots here that i'd like to display, followed by a couple snippets of code.

The top image is the appearance that I want. The lower image is the appearance I am trying to eradicate.

I scripted a custom shader for the stars, which is nothing more than a copy of the Particles/Additive shader that ignores fog. The fog turns the white sky particles black, which emulates the appearance of clouds blocking the stars. However, after 30-60 seconds of gameplay, the stars suddenly appear on top of the clouds. The only way to fix this is by restarting the particle emitter and forcing it to rebuild the clouds.

What exactly could be happening to cause this? I've looked through my particle emitter settings and am completely stumped.

Here's a copy of my shader. It seems to work properly.

 Shader "Particles/Additive (No Fog)" {
 Properties {
     _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
     _MainTex ("Particle Texture", 2D) = "white" {}
     _InvFade ("Soft Particles Factor", Range(0.01,3.0)) = 1.0
 }
 
 Category {
     Tags { "Queue"="Transparent-100" "IgnoreProjector"="True" "RenderType"="Transparent" }
     Blend SrcAlpha One
     ColorMask RGB
     Cull Off Lighting Off ZWrite Off
     
     SubShader {
         Pass {
         
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             #pragma multi_compile_particles
             //#pragma multi_compile_fog
 
             #include "UnityCG.cginc"
 
             sampler2D _MainTex;
             fixed4 _TintColor;
             
             struct appdata_t {
                 float4 vertex : POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
             };
 
             struct v2f {
                 float4 vertex : SV_POSITION;
                 fixed4 color : COLOR;
                 float2 texcoord : TEXCOORD0;
                 //UNITY_FOG_COORDS(1)
                 #ifdef SOFTPARTICLES_ON
                 float4 projPos : TEXCOORD2;
                 #endif
             };
             
             float4 _MainTex_ST;
 
             v2f vert (appdata_t v)
             {
                 v2f o;
                 o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                 #ifdef SOFTPARTICLES_ON
                 o.projPos = ComputeScreenPos (o.vertex);
                 COMPUTE_EYEDEPTH(o.projPos.z);
                 #endif
                 o.color = v.color;
                 o.texcoord = TRANSFORM_TEX(v.texcoord,_MainTex);
                 //UNITY_TRANSFER_FOG(o,o.vertex);
                 return o;
             }
 
             sampler2D_float _CameraDepthTexture;
             float _InvFade;
             
             fixed4 frag (v2f i) : SV_Target
             {
                 #ifdef SOFTPARTICLES_ON
                 float sceneZ = LinearEyeDepth (SAMPLE_DEPTH_TEXTURE_PROJ(_CameraDepthTexture, UNITY_PROJ_COORD(i.projPos)));
                 float partZ = i.projPos.z;
                 float fade = saturate (_InvFade * (sceneZ-partZ));
                 i.color.a *= fade;
                 #endif
                 
                 fixed4 col = 2.0f * i.color * _TintColor * tex2D(_MainTex, i.texcoord);
                 //UNITY_APPLY_FOG_COLOR(i.fogCoord, col, fixed4(0,0,0,0)); // fog towards black due to our blend mode
                 return col;
             }
             ENDCG 
         }
     }    
 }
 }