Nice shot. As far as the halos go, I can't really see too much in the posted image, so questions. Are you using the flash at full power? It may be that the halos are caused by flashback, or a direct reflection, from the flowers themselves. Have you tried shooting these with the flash at a lower power, say 50% and see if you still have this problem? I have a small Lastolite soft box that measures about 5.5 x 6 inches. I use that with my flash when I am taking some of my flower pictures. This softens the light and I have never seen this problem when using it. I almost always have my flash off the camera for shots like this one, so are you using the flash on the camera or is it off the camera so that it is hitting the flowers at an angle to the camera? Just some things to think about. Hope this helps.
WesternGuy