Hmm, the shadows do seem to be a bit distracting... Also, the highlights apperar blown, you might want to pull those down.
The image has a lot of contrast, but it doesn't really "pop" either, the busy background doesn't help either - for this I'd probably use something like your 50mm 1.8, preferably wide open or close to it.
Probably has something to do with the time of day too, it's better to take pictures on overcast days or earlier/later in the day.
Here's an old flower shot that I think looks kinda ok. t'was round middle of the day, but I had tree cover overhead to diffuse the light.
As for your picture, something like the following might look better, IMO:
What I did was open the image, and convert it to LAB mode, select the L channel and use shadows/highlights adjustment, with low amounts but large tonal width & radius.
Then I made a curves layer, and adjusted the L channel curve to reduce contrast, but kept the darks dark. also made a saturation boost in the A/B channels and turned the layer down to about 50%
Next I used a glamour glow filter to soften the image, but you can do the same thing manually by duplicating the layer, desaturating it, applying a gussian blur of about 10 pixels (for an image of this size; a bigger one would require more like 20+) and setting layer blend mode to Overlay and 20% or so opacity.
Finally, the image was a bit lighter at the top and darker on the bottom, so I filled a new layer with a gradient w/ black on top & white on bottom, put it into overlay and set to 10% opacity.
Edit: you might want to try blurring the background a bit too.