I've read some of the threads here about fungus. I used to own a Tamron 17-50mm f/2.8 Di lens, and it did have a tiny spot of fungus that I honestly think was a critter that moved. My well-aged Sigma 50-150mm f/2.8 HSM EX has a couple teeny areas on the glass inside the lens. In both cases, the IQ didn't seem affected but I never really used these shooting against the light. My newer Sigma Art 18-35mm seems fine - for now. I am just curious if others have found their third-party lenses are more susceptible to this issue than their Nikon glass. I suppose this isn't a big deal, but I could see it being one for sellers.