Beautiful flowers! The black background really makes them stand out, and brings out the great color. I like the arrangement, and the composition works well; the back of the flower and bud near the bottom add a nice touch.
As others have pointed out, the single light isn't very effective here. It doesn't really show off the three-dimensional form of these flowers. It shows a bit in the bottom orchid; you can see how the column and lip come forware and the sepals curve gently backwards. But the top two look flat.
The problem with flower photos in general is that they tend to get boring after awhile. It's easy to make them beautiful; the challenge is to make them unique and interesting. I'm not very good at it myself, but have found that little things can make a big difference. Here, for example, I think that just turning the middle flower slightly to the left would make it stand out more (although I may be wrong!).
I like the arrange of flowers here - its interesting. There's great detail ad nice focus - except in the bottom flower. I think the lighting is excellent and the black background works in bringing out the flowers.