Looking on the internet I found a different way of eliminating the stretch that seems to have worked for me.
Basically all I had to do was adding a "Texture Coordinate" node and connect "Object" to the "normal" of the Voronoi and Noise Textures.
Is this a valid alternative to switching off the "Auto Texture Space" option?
Thanks for sharing this tip ssilkkheldar! I'll have to remember that one. I've used Object coordinates before but didn't realize it was another option to bypass the auto texture coordinates.