I can imagine that in the viewfinder, you had the whole subject in the frame in shots 1 and 3. Whether or not that's true, they'd be better with the whole vase and the whole flower in the shot. The top of the white flower is clipped as well as the bottom of the vase. I would recommend reading up on and messing around with different methods of photographic composition. These are all pretty much centered in the frame, which is boring unless it reinforces some other element like balance. The first shot looks a bit soft, like it's out of focus or blurry.
I agree with the others that the tilt in the last shot is unpleasant. Keep shooting and posting!