some good points mike...my buddies red indicator on the co2 controller was so bright it was causing him problems...as soon as he covered it with black tape things smoothed out...this plant is finicky sometimes...especially chems and diesels..djAnother thing people forget is that the cheap silver ducting is a light leak waiting to happen. If you look at the normal silver ducting it has pin holes all through it and light can easily sneak though it. My last grow I got a couple nanners on some plants and I had to step back and think about what might of caused it. Well my intake that goes into the side of my tent I was running that silver ducting and there was light getting through it and that's where exactly the nanners where on the plant. I have since went and bought light proof ducting and in 2 days I'll be at day 50 without any nanners.
That was the first time I have ever got nanners in my grow was my last run unless like what was stated a late flower nanner but that's a plants natural instinct or it could be also from taking the plant way past it harvest date.
Another thing many people over look is small lights like say for example the orange light on my surge protector/timer that is enough to also cause hermies so you might want to put some tape over any small lights like that also. Also if you are growing in a tent those damn things come from the factory with light leaks so you have to make sure to cover all the stitching up around seems and zippers and everything else.