You have nailed it with the pink flower! The others are nice, my favorite is the orange bloom. The light on the blue one is just a bit harsh, but certainly okay. In direct sunlight , hold a diffuser over the flower. You might want to be a little more accurate with your selection of the flower when adding the black background. The pedals look a bit rounded where they should be sharp, I think. Try using refine edge in PS to perfect your selection. The latest version of PS also has a select background option which does a very nice job, too. Notice in the orange flower you let some of the green background peek through in a couple of areas in the lower right.
Keep photographing flowers. They are such beautiful subjects!
My favorite flower photographer is Kathleen Clemons. Note especially her backgrounds! Also on photos like yours of just the blooms, notice she fills the frame with the bloom, no need for any background. (BTW Your background with the pink flower works so well because it is subtle, yet shows the flower in its natural environment)