What is the ruling on saying "Masha'Allah" (as God willed) when remembering something during prayer, and saying "Astaghfirullah" (I seek forgiveness from God) when making a mistake in recitation, and is this considered an additive verbal act?

These verbal additions to the prayer do not invalidate it, even if done intentionally, and they do not necessitate the prostration of forgetfulness (sujud as-sahw), because they are remembrance of Allah Almighty and not human speech. Examples include saying "Amen, Lord of the Worlds" or "Allah is Most Great, supremely great." It has been reported that the Prophet (peace be upon him) heard a man say, "Praise be to Allah, abundant praise, blessed therein, as our Lord loves and is pleased," and he did not command him to prostrate.