Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.139A.

It is preferred to invoke Allah’s blessings upon the Prophets and angels separately. As to others than the Prophets, there is consensus among scholars that Allah’s blessings may be invoked for them along with others (but not separately). The statement of the Prophet, peace be upon him, has been cited above, “O Allah invoke blessings on Muhammad, the Prophet, and his wives, the mothers of the believers…” It is disliked, however, to invoke blessings for them on their own. For instance, one should not say, “Umar, may Allah shower His blessings upon him.”