Elven night vision

Headcanon: Although Calaquendi are overall taller, stronger, and in better shape due to being exposed to Treelight, they have worse night vision. Sindarin and Avarin elves can see things clearly with no more light then the stars drifting through the treetops, but an Aman-born Noldo has could see only slightly better than a Man.

This means there were probably quite a few survivors from Doriath, as although the Feanorian army was more experienced, they didn’t know their way around the caves of Menegroth and couldn’t see beyond the torches the carried with them.