I'm not sure what you want us to say beyond what you already identified. As you said, you applied to a low number of schools, many of which are highly competitive. While your application is good, so is everyone's who gets accepted to the competitive schools and there doesn't have to be anything "wrong" with your application to not get love from them. It just means others' applications were more compelling than yours. If you have to ask what you should send in an update, that means you probably don't have anything worth updating about--short of a publication, significant award, etc, there's little that one can send in an update that would move the needle.Stats: MCAT 519, GPA 3.7 with strong upward trend (3.4 freshman year > 4.0 senior year)
Undergrad: Majors in biology and Spanish, minor in Latin American studies (graduated a semester early - December 2018)
Gap years: Peace Corps youth development volunteer for nearly a year (evacuated due to COVID), now working as a legal assistant
Research: 3 years in undergrad working in developmental genetics lab (465 hours)
Volunteer: food pantry volunteer (180 hours), homeless outreach (260 hours), other smaller things as well
Employment: summer camp counselor, life guard, cvs retail associate - mainly in pharmacy
Shadowing: relatively minimal - 40 hours in the US-2 physicians, 40 hours abroad
State of Residency: Indiana
At this point in the cycle, I’ve had two interviews and one acceptance. While I’m very thankful to have an acceptance, my two interviews have been at the two schools I am least excited about. I only applied to 12 schools and quite a few reach schools, knowing it was possible I would only hear from a few. I have already received 3 pre-IIs (one yesterday from my #1 choice) and one pre-II hold (which is reportedly essentially a rejection), but still have complete silence from the other 6 schools since July. Is there something missing from my app that they’re hoping to see in an update or anything I can do at this point other than wait and see?
There's nothing wrong with being disappointed when you were hoping to go to a different school, but at the end of the day you're going to take your acceptance and run with it. So there's no sense in trying to do a post-mortem of what went "wrong" when there's nothing you can do about it now.