This is very nice. An attractive shot, good focus on the main flower with fly, and I especially like how the upper lighter background has formed that circular bokeh. This is a really good result from that lens. You were limited with how close you could be, and youve found the perfect distance.
You have received feedback on cropping, and this is of course connected to composition. It takes time to learn the concept of odd numbers, - I certainly didnt not know anything about this at the beginning, but when you try it, you can see it does help.
You decided to use -1 when exposing; one thing to keep in mind before deciding on exposure compensation is that the cameras meter will already take a bright background like this into consideration when you start; so reducing exposure is actually reducing even more than the camera has already dont on its own; so in general, - and by no means a hard rule, shooting subjects like this with a bright background needs either no exposure compensation, or a + EC to ensure the subject is not underexposed. The main subjects is a little underexposed, - but it actually works quite well. The mod I will upload has the flower exposed a little more.
The decision to use Manual white balance is the right decision, auto is often wrong, especially in warm light.
For me a square crop works well, and can make a very nice print. With a square crop, the subject also works well in the centre.
I have performed minor tweaks, - exposure is one, reducing the saturation of red and yellow is another (over saturation can cause loss of detail).
Mod2 is a framed version of mod 1
Hope you find this helpful,