Unsupported shader while building for ios

i am working on an ios app, it works fine in the editor but when i exported it to an actual device (ipad mini) xcode gave me following set of warnings

WARNING: Shader Unsupported: 'Standard' - Pass 'FORWARD' has no vertex shader WARNING: Shader Unsupported: 'Standard' - Pass 'FORWARD_DELTA' has no vertex shader WARNING: Shader Unsupported: 'Standard' - Pass 'SHADOWCASTER' has no vertex shader WARNING: Shader Unsupported: 'Standard' - All passes removed

WARNING: Shader Unsupported: 'Hidden/Dof/DX11Dof' - Pass '' has no vertex shader WARNING: Shader Unsupported: 'Hidden/Dof/DX11Dof' - Setting to default shader. WARNING: Shader Unsupported: 'Standard (Specular setup)' - Pass 'FORWARD' has no vertex shader WARNING: Shader Unsupported: 'Standard (Specular setup)' - Pass 'FORWARD_DELTA' has no vertex shader WARNING: Shader Unsupported: 'Standard (Specular setup)' - Pass 'SHADOWCASTER' has no vertex shader WARNING: Shader Unsupported: 'Standard (Specular setup)' - All passes removed WARNING: Shader Unsupported: 'Hidden/FXAA Preset 3' - Pass '' has no vertex shader WARNING: Shader Unsupported: 'Hidden/FXAA Preset 2' - Pass '' has no vertex shader

i have turned off all the image effects and removed all 3rd party shaders from the project but still the problem remains. Also, when i export this project to android, everything seems to work including image effects and overall lighting and reflections.

Please advice on how to stop these warnings for ios. I am using Unity 5.3.5