It is important to note the most significant improvements over the last cycle. This includes getting more clinical experience, community service, and completing critical courses. These essays are used to determine how well you have assessed your application's shortcomings, especially if you talked with advisors and other admissions staff before reapplying.
On the impact scale, you could mention an earlier submission but only if everything else in your application was competitive. It also presumes you never got an interview from the school.
Some secondary essays are hard to rewrite, but if the prompts offer you ample characters, I would consider rewriting those that show significant improvement from your previous application. Best to run this through your references and others supporting you.