Despite the description on the wiki, I have Cave Roots that are growing above light levels of 7 (at least up to 12). In other respects they are functioning as normal. This is in the Crucial 2 modpack, by the way. I will try to test this later with just Quark on its own.

I can confirm that this issue does happen with just Quark on its own (Quark-r2.4-308, AutoRegLib-1.6-47, Forge 36.0.58). Further testing suggests that the cave roots will grow no matter what the light is (pitch black or fully light, full block light or full sky light, still grows). I also realized during my testing that the cave roots will only grow on stone, which the documentation does not make clear.