Thanks so much for the replies Fuzz, Speede5, TopChed, Knightslayer! All super helpful information and gives me a real good idea of where to start, instead of just ripping out the ceiling.
It does seem like it could be moisture issues now that some of you mentioned that, as there’s not a lot of water, mainly bubbles pooling on the ceiling.
TopChed I did originally think something like a tiny leak in the showerhead, so I’ll explore that as well.
Ok noob it is CroFlames
Appreciate all the tips!!