I see that it was your second entry as a bloom photo. You would only get an acorn for the first entry for a bloom. But you can get more acorns for your first submitted photos of the 'Entire plant', 'Leaves', and other items on the list shown when you submit a photo. Like a close up of buds, stems, stamens.
Here is a screen shot. Lots of ways to earn acorns for the same plant.