I'm not replaying Xing at the moment because I'm still buzzy with the English translation. So I had to look this up in the walkthrough. From what you say I understand that you are in part two of the Itzali Point world, where you have to lit a number of fire scales to get 5 stone heads rising up from the water, but you do not get the 5th head up.
To get all 5 heads up, so you can hop to the rocky island where fire scale 8 is, you must lit the first 7 fire scales and it must be night and you'll need the stone statue from the chest. In daytime you can set 6 of the 7 fire scale on fire, but to reach the 7th scale, on the island were the chest is, it must be night because the two pillars to reach the chest island are moon pillars. In the chest you'll find a stone statue. You need to put that stone statue on the light scale, in nighttime, and all the 5 stone heads will be up, like a stairs, and you can hop over them to the rocky island to fire scale 8 to continue your way. Hope this helps