You can write about anything you want if you do it well. But how does that talk about how you fit on campus as a student and shows your strengths and curiosity? I would pick 3 topics of interests. You already have 1 so pick 2 others. Do a few rough drafts. Have a teacher/counselor read them over and see what hat the comments are. The problem is health issues become cliché. They read thousands of these so how does that separate you from the pack?. I am happy your doing well but how does that tell me how your going to be engaged on campus?
So…this is where you let your counselor write about what you overcame and you concentrate on the “Why” this school questions. It’s much stronger if it comes from your advisor.