Hi,
~I could be wrong about this, but I think it’s correct~
the reason you see a drop from ~120 FPS to the mid 50s is because lighting requires shaders, which will cut the FPS down to about 50 on most graphics cards, but note that you can probably do infinite lighting without losing the 50 FPS you did before, also your graphics card (if any) may likely have little to no shader support, which may also cause the problem