Mottling is a natural condition where the plaster has several greyish "shades", kind of like "white clouds". Mottling should not be confused with actual staining. Mottling is very common and usually not a concern. Hope this helps ....

what kind of pathogens normally cause mosaic and mottling

Mottling occurs when the dye migrates during the granules' drying process.

Yes, mottling can come and go. A person may mottle in the legs and feet if they are sitting up but once laid down this discoloration can cease. Sometime if a person is put on oxygen this may decrease mottling for awhile also.

Fluoride