السلام عليكم ورحمة الله وبركاته Ustadh, I thought that the ي in عَلَيْهِمْ in Fatiha had a kasrah so I elongated it in prayer. Is the prayer invalid and should I repeat it?

Ustadh AbdulAziz al-Haqqan

This is Waswas, and you need to ignore these thoughts and tackle the main problem, which is these compulsive thoughts.