First of all, make sure you haven't gone down the second blue swing vine to level 1 and the purple bulbous plant; that's part of the next puzzle.
See any more purple reflectors?
Point the reflector on level 4 (the level you should be on) to the sunflower in front of it. You can take a peek in the sunflower if you want to see what the purpose of this puzzle is.
The sunflower is aimed at an empty pool
I see what it's pointing to; how am I supposed to get light on it?
