My plants have been grown from seed indoors, and I am now about 10 weeks into the grow. Every once in a while, I notice leaf tips missing, holes in leaves, and twisting or other signs of damage. I have looked at damaged leaves and I have not seen any insect or insect faeces. I have looked under 60x magnification on both sides if many leaves and couldn't find anything. What could be a cause of this? It hasn't been getting worse over the last 10 weeks, but it seems to happen on smaller fan leaves and in more shaded areas of the tent. Overall 95% of leaves appear healthy, so im not too worried, I'm just wanting to know what is going on.