Mold is very bad for photo manufacturers. If mold takes hold, it can leave blotches on the material that will not come off. Mold loves gelatin! Kodak has bacteriostats in everything as do Ilford and other companies. They are there to combat the growth of mold and bacteria. We had yearly scrubdowns at EK because sometimes mold just took a foothold.
So, something is amiss here, as I know that Fuji uses a bacteriostat. This is a very bad and unusual problem that I would inform the dealer about. If the rest of his stock is contaminated, it can go bad as well.
Watch out for cross contamination of other products you may be storing and watch out for it in any food stored with it as well.