I took a look at some Osteospermum Jucundum that I have. Now if you do not see any mites or insects on your plant this is the best explanation that I can give you for what is going on. Currently, you are growing these daisies outside where they can be pollinated by insects. Once the flowers are pollinated the plant is not focused on maintaining the flower and instead turns its energy to seed production, which takes place in the center of the flower. This causes the outer edges of the daisy to wilt which are no longer being supplied with nutrients. In one week the center of the flower produces seeds. If you want to get more flowers, cut the flowers off that do not look pretty. This will cause the plant to become fuller and produce more flowers.

I took a look at some Osteospermum Jucundum that I have. Now if you do not see any mites or insects on your plant this is the best explanation that I can give you for what is going on. Currently, you are growing these daisies outside where they can be pollinated by insects. Once the flowers are pollinated the plant is not focused on maintaining the flower and instead turns its energy to seed production, which takes place in the center of the flower. This causes the outer edges of the daisy to wilt which are no longer being supplied with nutrients. This can be seen in all of the daisies that you have pictured. In one week the center of the flower produces seeds. If you want to get more flowers, cut the flowers off that do not look pretty. This will cause the plant to become fuller and produce more flowers.