I was growing sunflowers in my garden for a wedding and they were beautiful. I checked them everyday but it seems like within a few days they started getting spots on stalks and leaves started to turn a d the brown spots were all over entire plant. I dont think its rust or powdery mildew. No visible bugs. Could it be phomopsis. Thank you
It looks like you have Alternaria on the leaves, and Botrytis on the flowers.
Neither are uncommon with the extended wet weather we have had.
Here is a page on Botrytis: http://extension.umd.edu/hgic/petal-blight-botrytis-shrubs