When I first began collecting acetates I found that condition varied wildly. Some crack, some peel, some flake, discolor, fade, and some basically turn to dust. I had already seen hard finishes like polyurethane and varnishes do all of the above. But there was also sometimes a whitish discoloration, it looked kind of like mold but what the hell kind of mold would grow on acetate?
An acetate (also called a ethanoate) is either a salt or an ester of acetic acid. Acetic acid is a weak organic acid found in vinegar. In this case it refers to Polyvinyl acetate (PVA) as the substance on transcription recordings. It has a Ph of 7, which for reference is about equal to that of distilled water. So despite appearances it's acidity alone will not kill germs dead. but nonetheless it's not mold on that disc. I don't' want to get too bogged down in the chemistry but, PVA is painted on cheese wheels to prevent mold growth. Just make the leap of logic that mold is very unlikely. The more liklely culprit in these cases is palmitic and stearic acid.
More acids? Yes, more acids, specifically fatty acids. Stearic acid has a Ph of 5.5; Palmitic acid 5.5. Neat fact about Palmitic acid, it's an ingredient in a formulation of napalm. Their about as acidic as coffee. It's not a very powerful acid but since it's a fatty acid it tends to cling and over time it eats into the laminate. Where does it come from? It's in the natural oils left behind in your fingerprints and dust because dust is made mostly of human skin. Those fingerprints also contain myristic acid but it has a ph of 6.5 or so and it's barely acidic at all. The Palmitic and Stearic acids are the real culprits.
So keep your records clean and keep them in good acid-free paper sleeves. I buy mine from Nauck's Vintage Records.