I've been trying to clean the elements of a 70s vivitar 600 using fibre cloth with hydrogen peroxyd and then wet glass tissues for the finish, but most of whatever was there is still there. It is no fungus or dust or cleaning marks. What is it ? And how can I get rid of it ? I ve been quite forcefull while cleaning, seeing that not much improved... I had the doublet out and tried my best on both elements. Thanks for your opinions. The pics are cellphone but they show enough.