Does praying for oneself or saying "Masha'Allah, there is no power except through Allah" after finishing the recitation of Al-Fatiha, while the Imam is reciting some verses during congregational prayer, invalidate the prayer?

What you did by supplicating and performing dhikr after Al-Fatiha does not invalidate the prayer. Some scholars have even stated its permissibility, such as Al-Hattab Al-Maliki in Mawahib Al-Jalil, quoting from Al-Tiraz: "One may supplicate after finishing Al-Fatiha, if he wishes, before the surah, and the righteous have supplicated." And performing dhikr out of its proper place does not invalidate the prayer.