There's also one level (1-3) that's very wide, so when you're at max light expansion, it looks like there's still more below to expand to, but there isn't. (But if you're missing eggs, it's probably the Egg Clowns, as mentioned.)
But as far as light goes, if you got the button that lets you end the level, it means you've reached the max light expansion level, so you're definitely not missing anything.