wheat sourdough bread?

I'm one for sourdough bread, and I hafta say - I make a tasty bread!

However, with my most recent batch, I used wheat flour instead of unbleached flour, and the loaves turned out smaller than normal, had a difficult time rising, and didn't have many bubbles within the bread.

Does anyone know if wheat flour is meant for sourdough bread? Or, rather, that sourdough bread turns out as it should using wheat flour?

(Does it even make a difference?)