1) Too busy. Assuming the flowers were your intended subject, the background is way to distracting. Since your out at day light, use a larger aperture and and faster shutter speed, along with getting closer (focally or physically) to your subject. This will blur out the background and draw the attention back to the flowers, making them pop out.
2) There really is no obvious subject here, which causes your eyes to just wander.
3) The various angles and lines make this one work well. Easily the best out of the bunch IMO. The lighting plays very well off of the finished wood.
4) This one again feels like it has no subject, or better yet, too many subjects. Pillars, benches, man reading, buildings, its overwhelming. Try to decide what your subject is in a shot before shooting it, it will allow you to better frame and expose the photo to benefit that subject. After all, you wouldn't right a novel with out a character, would you.
5) As far as shooting fish goes, I'm clueless. The only thing I can say is the one fish in the background sort of looks like hes dead. That's all I can think when I look at it.