Your pink stains, if it is what I think it is, are typically associated with the presence of vinyl coated/impregnated products. I and many others have had to contend with this nuisance stain on our awnings. It is not mildew. It's a by-product (poop) of bacterial micro organisms. The by-product manifests as a dye that is soluble in the plasticizers commonly found in vinyl coated products. The marine (boating) crowd are more familiar with this. We've had some success at removal with a diluted mix of household bleach but again, if that's what is staining your ceiling/s, where's the vinyl component?