You are asking about how to change the past... why?
No, your app with 2 years of ECs and clinical experience will not have as much on it as someone who has 4 years worth. Does that mean you are doomed? Absolutely not. You have PLENTY of time to beef up that section, and plenty of time to find ways to make those 2 years of experience somehow more distinguished than people with 4 yrs. Are you that perfect applicant that did everything right and was totally on task from day 1? No--but neither are most of us. Don't stress. You're FINE.