creating a shader that is compatible for smartphones

Hi there, I have created a shader that works great on windows but that does not function correctly for smartphones. The shader is ment as a poison effect shown in the image below:

When I create a build for my phone the correct poison color is being displayed but the screen waving effect seems to be completely missing.

Here is the shader code that creates the poison effect:

 fixed4 frag (v2f i) : SV_Target
             {
                 fixed4 col = tex2D(_MainTex, i.uv + float2(sin(i.vertex.y / 40  + _Time[1]) / 35 * _t, sin(i.vertex.x / 40 + _Time[1]) / 35 * _t));
 
                 float _RedOverTime = 1 - (_t / (1/(1-_RedFactor)));
                 float _GreenOverTime = 1 - (_t / (1/(1-_GreenFactor)));
                 float _BlueOverTime = 1 - (_t / (1/(1-_BlueFactor)));
 
                 col.r = col.r * _RedOverTime;
                 col.g = col.g * _GreenOverTime;
                 col.b = col.b * _BlueOverTime;
 
                 return col;
             }

_t is a value between 0 and 1that determines the amount of screen waving and the amount of green that is being displayed in the game.

Any help would be really appreciated!