Should I retake a 35 ACT if I got a 33 in science?

In general, I would say NO…but I take it you are a junior? My understanding is that starting next year, you can re-take just a single section. (One year too late for my student, sad to say!) So I don’t see any harm in retaking just science if you want to see if you can raise that score.

https://www.act.org/content/act/en/products-and-services/more-choices-for-the-act-sept-2020.html