I'm new to compositing, so I'm unsure how simple this problem may be to solve; apologies in advance. Anyway, here we go.
My scene was too large to render, so I separated it into 3 different Render Layers-
The three layers seem to be rendering correctly, lighting and all, as the render progresses; I can see each individual layer as it should be, and have my Alpha Over nodes set up accordingly-
However, the final render saves to my computer as such-
Some final notes; I have transparency selected in the render panel, the render also doesn't work if I remove the "File Output" node, and I have it set to GPU render (though it's the same result even if I change to CPU render).
What am I doing wrong!?