Hi Hannah, I love the coloring of your pictures with the bright pink, greens and yellow. I would suggest using the rule of thirds when photographing flowers instead of centering the focal bloom. Also be careful of the placement of flowers in the background that might appear to merge in odd ways with the flower in the foreground. You don’t want your flower to look like it has an odd lump only on one side! Here are a couple ideas:
-Get closer to the ground and shoot in portrait to get more flowers in the background.
-Lie on the ground and shoot in portrait to photograph the stem, stamen and blossom. You could use a dark bokeh, or include trees, more flowers, or sky in the background.
-Shoot from down low and use the sky to silhouette the zinnias.
-The closer you get to the blossom, it might become more easier to get the flowers in the background to align where you want them to.
Overall, I would recommend using the rule of thirds. You have some good ideas going and I think your third photo has the best composition, although the lighting in that one isn’t as good as in the other photos.