I'm having trouble following that you got an F because you didn't drop a course officially. My gut reaction was that it was your responsibility to make sure you did all the official paperwork.I didn’t do well in my science courses in undergrad many years ago.
I have 3 F's. 1 F in biology because I chose not to take the final exam. 1 F in biology at another school that I dropped early but not officially so they gave me an F. 1 F in a foreign language course that was study abroad that I dropped before the course began, but again because it wasn’t dropped officially, they gave me an F.
Should I be explaining these red flags in my secondary essays? What should I say since two of them were not deserved?
Do not explain anything unless specifically asked.
Explanations usually end up coming across as excuses.