Don't fret over this. Ultimately, if they want you they will let you know. A note or an email won't change that, it only adds to the endless list of things admissions has to open and file. I'm sure they would rather nothing be sent. It won't help in any way. Tufts receives well over 4,000 applicants a year, and out of those who interview, even if it was 2,000, if they got 2,000 thank you notes or emails it just becomes a hassle.