All the gear and no idea springs to mind.
Having spoken to k rend on several occasions they recommended using Benz products lightning clenze to be precise which is a biocide , it’s not an acid as @Dave B has already stated , as an external Cleaning company I would have thought you would have know the difference and how to use the various products correctly . Hypo is not a cure all for cleaning it’s only suitable for organic or bacterial growths it won’t clean/remove carbonatious deposits .