#1 - Subject is centered in the frame (static, boring) and the sky is all blown out and is pulling the eye away from the main subject. Next time try to fill more of the frame with the subject and watch your backgrounds.
#2 - Subject isn't centered (which is good) but what is going on with the dark areas? Did you do that in PP or did you flash the flower with a off-camera flash using a snoot? Don't care for the upper petals of the flower going into the dark. Too much dark space on the right.
#3 - Subject isn't centered (which is good) but I don't care for the leaves in the foreground that is partially blocking the flower. Having the bee there is a nice touch. The sky is too blown out and distracting. Colors are nice and bright.
#4 - Nice use of backlighting to highlight the hair. But the red mat they're standing on is causing a red color cast on them from head to toe.
#5 - Really nice B&W conversion. Composition is good and I like the use of the shadows on the ground. My favorite of the bunch.