Fog refresh rate on iOS

Our game is an endless runner setup and we’re currently using fog to hide objects in the distance that haven’t loaded yet. It functions perfectly on the computer, however when we build it to a device or run it in the xCode iPhone simulator, the refresh rate of the fog becomes very low. This results in the player ‘catching’ the fog instead of it always being in the distance, which is ruining the way we’re handling shadows etc. We’ve had a look around but can’t seem to find any reason why it’s refreshing so much slower on the phone, nor can we find a way to forcefully increase it.

Has anyone come across this issue before, or know a way to enforce a specific refresh rate for fog on a device?

We are also making an endless runner type game for Android. We are encountering the same problem. We’re using linear fog to hide objects in the distance, it works perfectly on PC within the Unity Development Environment, but when we install it on an android device it look like our character is catching up and coming out the other side of the Fog and doing this continuously.