Scope the underside of the damaged leaves, right along the veins, with at least a 50X magnification. You will see them. You haven't heard about them yet, because most of the people on this forum, that know what they are doing, rarely help. The rest are quick to give bad advice, based off of pictures they find on the internet and have no actual real world experience, with the problems users may be having.
I just happen to have experience with almost every pest, that likes to munch on plants. Been growing various plants with aeroponics, for the last 20 years.