Foliage lighting problem

I am getting a big problem with the lighting. When I have a smaller amount of foliage, none of it is visible when I get rid of the directional light.

When I have a lot of foliage, it is for some reason visible when the directional light is gone.

How can I fix this

So you have 2 directional lights and when you remove one of them, parts of your foliage dont render.
What are the properties of the remaining directional light? is it Static/Stationary/Movable? What are the shadow properties?