Just got a Minolta XE-5 off Ebay today. When I removed the lens, this is what I saw on the mirror. I'm new to collecting and shooting vintage cameras so this is new to me. Is this just water damage? Is this fungus? What's the worse case scenario? I want to try and clean it but I'm afraid I would make it worse. But if left unchecked, is this going to be a problem? I'm trying to shoot a roll right now and get it developed to see if it effects the photos. But I'm more concerned about what it will do in the future if left unchecked. Thank you guys.