I don’t think you should because that one notification is a bit off to me. Firstly, sending acceptances on a Sunday is kinda odd, especially for Brown. Second, Brown isn’t known to stagger their responses at days intervals. It’s been two working days since that acceptance and still crickets. Usually, waitlists and acceptances go out about the same time, and rejections follow shortly after—same day or next day (I know because I was high on the wait list last year. Also, notice that poetry notifications this year followed this pattern). I’ll say until you get a response from them, still hold on to that delulu. Just saying.