Again, being rescinded is unlikely. Your GC didn’t suggest you send an email, but you want to anyway, just in case. Did you say this to the GC?
If the GC seems unwilling, I see no harm in you sending a short email. Keep emotions out of it as much as possible. You could say something like this:
Dear Mr. Jones (your regional AO),
In my final transcript, you will notice a grade drop in my last semester. I take responsibility for the change in my grades and want to explain the situation.
My grandfather has been in the hospital, very unwell, many visits to hospital, interfered with ability to complete work. Strain on family (or whatever your situation is, but stay focused and keep it short.)
I am doing all I can to improve my grades. I have gone to extra help with teacher, etc…
I realize that my current grades are not up to the standards of CMU. I intend to make use of the tutoring center and Professor office hours while I am at CMU, etc… Please let me know if there is anything else I should do at this time.
Thank you for taking the time to read this.
Sincerely,
Johnny Smith
555-555-1234
In your shoes, I would send an email. You’re already in, and it can’t hurt. At the very least, it should pre-empt you getting a stern email from them, which seems likely with three C’s.