Thanks for the response, but unfortunately no processes or background processes are out of the ordinary or using too much memory. For more detail, the frame drop appears to begin when I either press a button on my keyboard or my controller.
I have been playing for a while and even played a lot today, but when I came home from dinner I found that I am having serious fps issues. I have never even dropped a single frame in hundreds of hours of playtime, but now the game is so slow it is unplayable. I have restarted, reinstalled...