Thanks for all the feedback!
I try to avoid putting in health bars unless I need to, but I agree that the purple, spinning turrets don't give enough feedback about how much damage they've taken in particular. With 15 hp, they require nearly two seconds of direct hits to destroy, even if you don't miss. I wanted to do some sort of "damage stage" system where they'd get more beat up after taking hits, but since I didn't have time for that, yeah, I prolly shoulda just done floating hp bars.