Lighting problems on certain systems and with Post Processing Quality levels of 0 or 1

As the title says, on some systems, everything works great, but on others my players seem to be plunged into darkness.

My levels are lit this way so far:
I have a MoonlitNight BP that has a DirectionalLight component that moves 180 degrees over the course of the level. (Basically you have from the time the Moon rises until it sets to complete the level.)
Inside this class there is also an AtmosphericFog component that gives the sky around the level.
Separate to this I have a SkyLight that just provides some global ambient illumination (Just something to keep my walls and ceilings with some minimal light value so they’re not black.)

This works great on my machine and some others, but on a few other machines, the only light that seems to be there is my player’s flashlight and the directional light.

This is my working lights as described above:
nevermind… Once again I’m given a Database error when attempting to upload an important image.

This is my lighting without the skylight:

This is my lighting without the skylight, and without the AtmosphericFog component:

Well, I WAS going to ask if there’s another way I can go about getting the results I need that is going to be more universally acceptable with more video cards. Obviously there is something here that really could (and should) be done another way.

Also, and THIS IS IMPORTANT: My level is 100% generated at runtime so I cannot bake any lighting data or do any of the other neat and fancy lighting stuff.

I’m going to try to get my working lights screenshot uploaded another way. It was taken and created the exact same way as the other two, but I get that stupid database error a LOT when trying to upload images.

Okay, here’s a copy of the working lights that I’ve been trying to upload for the past 20 minutes. (Eventually I just had to take a screenshot of the image opened up in paint and include a bit of the paint border around it for it to post. Odd thing is I’ve had to do this before. I do NOT understand this.)

Obviously I need another solution to get this result, or see if there’s another setting somewhere I can try.

I really need the help of any of you dynamic lighting gurus.