Game Scene becomes darker than it should be.

I’m using Unity 5 and the game becomes really dark for some reason.

Playing from "Forest" Scene

From the top you can see the lightning is “Normal”.

Click on the button to go to main menu

I click on the button and I’m at main menu

Go back to game from main menu

I press play from main menu screen, and the screen is darker than before. The colour sorry, it’s as if there’s a horrible dark tinted overlay. I did not tinker with any settings, and yet, this problem arises.

Major Edit:

I’ve build the game and the problem disappears. The colour is normal in both scenes.

So it appears, this dark overlay only happens in the game preview, now in the final build.

have you menu a transparent background layer, what you forget to remove if you close your menu?

i think it is due to the skybox light.
Change/Clear the skybox and check the scene.