Cs and Bs won't help, but you can do better as a MS2.
A bigger problem might be Step 1. Marginal MS1-2 grades is a strong predictor of a poor Step 1 score. Figure out why you did poorly as a MS1, fix the problem as a MS2, do well on Step 1 and you'll be fine. Lots of people have been where you are and things worked out.
Derm is probably out of reach but anesthesia isn't.