Sounds like you’ve already notified schools before dropping it, which is the correct action.
Yes, they can rescind an offer for substantive changes in an application. A grade below a C and withdraw/fail are very common reason, along with legal troubles.
If a school that you want to attend says your offer will be rescinded, try to get through the rest of the year. With a 93 more than half way through the year, keeping it at a C or above should be possible.