Shadow getting lighter when I use EffectComposer

I am using shadow material and plane for shadows. When I add effect composer the shadow color becomes lighter, from a dark grey to light grey in my case.

i am using GammaCorrectionShader, TexturePass, ShaderPass and OutlinePass in the effect composer.

Appreciate any help thanks!

My suspect is the use of gamma correction. This is just a feeling.

Is this related:

Effect Composer Gamma Output Difference