Marshland

Found the gem to heal the frog and the shell the instrument, but cant use either of them ...nothing else lights up. What am I missing?

If I remember correctly, you had to turn the stone to water (healing water). At some point you had to clean the shell to make the instrument, then study it and have it played so that it affected the clouds. Did you collect the mushrooms for the cauldron? And fixed the wtaer system?