What's the problem with them?
Both the 100 and the 135 have got slightly cloudy patches behind the front element (I got them both recently, 2nd hand from different people, so it's not caused by me storing them badly or anything like that). I don't have any results developed yet, so I don't know if the image is affected. The 50 (another 2nd hand one, it came with a camera) is very dirty with lots of dust and fungus spots on the elements, so I thought that one would be a good one to try cleaning first as practice, seeing as it's worthless anyway.

Alan