Thanks @jyotu it's in the sun.i will try to trim more so it can get better ventilation. I noticed it like that after i brought it home from the dollar store. That's why i never planted it with my other two.
Haven’t had to deal with it in a while so I can’t recall if it was the vinegar or baking soda I used, but here’s an article. https://www.growingagreenerworld.com/controlling-or-eliminating-powdery-mildew/