Collect at least10 coins (there are 11 total before the "Point of No Return", which is the end of "Forbidden Area"), buy "All the fish" from Alba, throw all of the fish (fish x99) into the Central Tree (a mirror in the Tree is in fact a door, but you need to visit "Red's Treehouse" for MC to be able to check closely). Then, proceed with the Fairy Ring area as usual. At the end Aoi will find your fish scattered around the Mouth and throw it all in for a good measure. Turns out, Lacie has bought just enough fish!
The ones you are missing are most likely the ones in the locked area. Not the first topmost path, but follow the petals further to the right until the second one — up and to the left — and the third one — the exit path, but once you see the bush in front of you, go left. Also follow the path to the immediate right as you enter. Once you get them, you have to turn back out, or you can never return.