if you remove fan leaves during flowering, only remove those that are blocking light from reaching the inside of the plant. never remove fans off of the tops or your main kolas.. when you leaves start to gold from the bottom up, its ok to remove those as soon as they start to turn as they are going to die in a day or two anyway. always remove leaves that are more tha 50% damaged as they generally arent adding to the growth of the plant anyway.
i always check leaves with a hand loupe before removing them during flowering anyway. if they contain trichs, i leave them on anyway. i remove all fan leaves only 24 hours before harvest.