I think it could be bacterial leaf spot disease but need more information to further diagnosis.
1. Is there any symptoms on stem and petiole?
2. How is the weather condition?
3. Are the seeds certified?
4. How do you water the plants?
5. Did you grow any crops last season in the same area and did you have the same problem?
Also, according to studies, copper fungicide should not be used during flowering stage in solanaceous crops.
For more information on disease