If I recite the Fatiha and a surah in prayer, then re-recite the Fatiha due to a deficiency in it, but forget to re-recite the surah, must I re-recite it?

All praise is due to Allah, and prayers and peace be upon the Messenger of Allah, his family, and companions. To proceed:

It is sunnah (recommended) to recite a surah after Al-Fatiha, and it is not sufficient if recited before it. So, if the surah is recited before Al-Fatiha, the sunnah is not achieved, and one is required to repeat it unless they have bowed. If they have bowed, then they should perform the prostration of forgetfulness (sujud as-sahw). The recitation of a surah after Al-Fatiha is a condition for its sunnah to be realized, and it is not an independent sunnah. Repeating Al-Fatiha instead of a surah is not sufficient because it is contrary to the Sunnah. Therefore, it is recommended to repeat the surah after Al-Fatiha. However, if it is omitted intentionally or forgetfully, the prayer is still valid.