Why such a shallow DoF? The 50mm should provide a greater DoF than the 100mm at f5.6, when focused at a similar distance. This looks like much less than life-size, so I'm guessing you were a good distance away.
Is this the effect of the Raynox? I've heard of it but have no idea how it functions. There seems to be some optical quality loss at the flower tips. I am not a fan of adding extra optics in a lens' path... If you wanted to go macro with the 50mm, then I would have suggested either extension tubes or reverse-mounting it.
Where's your 100mm? I miss it.