Its a difficult ballance when you have such a bright yellow flower and then a very dark center. You have to trade off one color for the other and I think you chose the right ballance for an overall good exposure. The lighting was just a suggestions if you wanted to bring out some of the center detail without blowing out the color.
Something like a glow, like the sun coming through and a ray hitting the center of the flower. That would make the detail of the center show more but keep from making the yellow wash out. Just a thought???