They are all there and what's strange when I run the game the log complains about some missing textures, but not the actual Quadrum ones:Quadrum textures are in a really strange place, you may have deleted them by accident - check for Regrowth\minecraft\config\Quadrum\block\textures (contains dead wood tree textures) and Regrowth\minecraft\config\Quadrum\item\textures (contains deadwood, plates and a couple of other things). Those folder should contain small .png files which are the textures from quadrum.
I fiddled with Quadrum config file a bit (well, switched all the available options to true) but that didn't help at all. Now I'm sad.
Edit: The textures aren't even really missing, it's like it uses top left 2x2 px area of the texture (and with dead planks they are transparent).