its not a mould as such, more like a but gundgy
i know Ken Wainwright queried it once when the new Final Phase was introduced by Solutions and he put it down to that.
maybe just need fresh every - have tried a sanitiser but still get it a bit
maybe try a different rinse - whats a good economical one? I like DFC105 but not sure if thats ok if putting protector down after as its not acid even though it dries neutral