Blocks drop Mushrooms, Chorus, Noteblocks

First reason

If you have EmeraldEnchants2 installed read this

Second reason

Did you delete the custom blocks folders in your world? Don't do it.

If you delete it you lose every custom ItemsAdder block data in the world.

Third reason

Corrupted chunk. This can happen if you:

killed the server while it was saving an IA region file
full disk problem which blocked saving of files
reloaded the plugin using Plugman or similar
reloaded the server using /reload command