Did Ammar ibn Yasir and Adi ibn Hatim declare Uthman and Talha as impious?

There is no accurate and authenticated information about the status of Ammar and Adi with Uthman - may Allah be pleased with all of them. The creed of Ahl al-Sunnah wal-Jama'ah is to refrain from delving into the details of what occurred between the Companions - may Allah be pleased with them - as they must be mentioned in the best light, and one should refrain from discussing their disagreements, and harbor good thoughts about them, considering them as mujtahideen (those who strive to reach a correct legal opinion), among whom are those who erred and those who were correct. Ahl al-Sunnah wal-Jama'ah do not believe in the infallibility of any of the Companions from major or minor sins; rather, sins are generally permissible for them. However, they possess merits and virtues that necessitate the forgiveness of anything that may emanate from them, just as they are the best of generations. If a sin was committed by one of them, then he would have either repented from it, or performed good deeds that expiate it, or been forgiven due to his precedence, or through the intercession of the Prophet, peace be upon him, or been afflicted with a trial that atoned for it.