@apkley, luckily it wasn’t that. I’ve tried getting a good picture of it, but this is about the best I can do right now.
Basically, really tiny air bubbles that got trapped. In some cases they made it all the way up and left a little pin hole which was taken care of by the second and third fill coats.
Unfortunately though, it isn’t isolated to one patch. It isn’t over the entire shell, but there are enough to make grinding and patching not worth the effort at the end of the day.
If I were to do it all over again, I’d probably consider doing a pre-coat of epoxy. Though, I’ve read that it doesn’t always prevent it. In either case, it seems to be isolated to the #1 panels, so while I’m not ‘happy’ about it, I think I can live with it painted. 😉