What went wrong with our Lighting / Material setup?

Hello guys,

We are approaching the deadline of our game production and need urgent help.
Most of the textures look really odd, especially those exported from the 3rd party program "Substance Painter".
As advised I'm using the standard shader with the same setup as in their documentation.
Yet the results I'm getting within our game scene are vastly different.

[img width=400 height=213]http://i.imgur.com/AIUrCVj.png[/img]
[img width=400 height=190]http://i.imgur.com/l05Ej7V.jpg[/img]

[img width=400 height=468]http://i.imgur.com/49pgPCv.png[/img]
[img width=400 height=361]http://i.imgur.com/xFfTa4f.jpg[/img]

http://imgur.com/a/3ygR4

Using deferred rendering and a linear as instead of the gamma color space didn't really help at all.

http://imgur.com/a/TPKtr
Here's a screen of the project setting comparision
Is there any unchecked box or such which leads to my problem that becomes apparent to you?

Best regards,
Withi

 

For anyone encountering the same issues: We somehow forgot to set a reflection probe within our scene