All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Since you had sexual intercourse with your wife after the bleeding had totally stopped, and after she had performed Ghusl, then you are both not sinful even if she had bleeding again because when you had intercourse with her she was pure, and you both were not obligated to wait for more days. Rather, whenever a woman sees purity and performs Ghusl, it becomes permissible for her husband to have intercourse with her.
Besides, this bleeding that your wife saw is ruled to be menstruation if it is within the time-period that can be considered as menstruation, like if 13 days or more have expired between seeing it and the interruption of bleeding prior to it, then it would be considered as a second menstruation. But if less than 13 days have expired between this bleeding and the interruption of the bleeding before it, then if this bleeding is added to the previous bleeding along with the period of purity between them and their totality do not exceed 15 days, then it is also menstruation, otherwise, it is bleeding outside the monthly period.
For more benefit, please refer to Fatwa 129256.
Allaah Knows best.