I would say this is a sure-fire way of destroying an acetate , the bond between the lacquer and the metal is not strong enough to withstand the use of PVA which will bond too strongly to the lacquer more than likely removing the thin layer along with the dirt and mould , especially if there is any microscopic debonding already occuring ... which in the case of the discs shown is very likely.
Weak soap solution using cold water ( warm water will soften the lacquer ) and a very gentle touch is the way to go.