I should add that the FC paint was their 100% acrylic satin house paint.

buy bleach and a powerwasher, sorry but it's the nature of the beast.

Get a plastic pump-up garden sprayer and apply a 25% bleach solution to the ceiling and mildewed areas, wait 15 min and hit the bad areas again(if any remaining). Rinse with a garden hose. You may be able to stop there. If not you had to kill the mildew anyway.

I've had good luck with M-1 mildewcide additive in paint but it doesn't last forever. As far as paint goes any manufacturer's best acrylic should be fine on a covered ceiling. Even the best from the big box stores.

We have the same issue. The white beadboard ceiling shows everything. The plan is to clean it as suggested above, and then we will repaint it a light grayish blue, probably in Duration semigloss so it is very washable.

Mildew sealer would be a great product to use before painting exterior in the south. After beaching substrate, a necessity before painting exterior, apply a thin coat of this clear product. It provides a mildew-free surface to hold the top quality Farrell-Calhoun paint. Embedded mildew spores cause may reoccurring mold/mildew problems. Mildew sealer is made by amteco. Farrell-Calhoun has everything I needed!