In parallel, from a suggestion, I started a new small batch in a jar. It's much cuter.

That sounds like much less of a hassle (and less wasteful, too)! I might have to give that a try. Thanks!

Will do! For the pint jar approach, can you do that starting with just flour, no commercial yeast/donated starter (which is what I'm attempting here)?

I think this is just for the very beginning? (I'm following the steps in a book). Once it gets going, it gets trimmed down quite a bit. Also, the tub is way bigger than necessary, it's just what I have.

Thanks for the reassurance :). I'm not super worried, I just didn't expect day 2->3 activity to be so much better than day 3->4 activity when I did the same thing both days.