Custom Biomes and Blocks not working in The End

So I have been modding in all my spare time for about 5 days, and I've run into a few roadblocks (no pun intended). I have created a custom biome which should spawn in The End, but it doesn't seem to generate at all. Additionally, one of the blocks for said biome is an "Endstone Grass" which is just endstone with grass on top. However, I am unable to place plants onto this block. Any help would be greatly appreciated!