Leaves problem

You have a pest problem. You have clear signs of thirp damage on the tops of your leaves. On the back of the leaves it appears to be thirp fecies. You have a few options. You could check out natures good guys and get some predatory insects that feed on thirps. The quickest method would be Growers Ally Crop Defender 3. Its an all natural insecticide/anti fungal spray. Made from oils like rosemary. The 8 oz concentrate is the best bang for your buck. But if you only have a few small plants the premixed spray should be enough for a couple treatments. The product can be used inside and outside as well as in veg and flower. Hope this helps. Happy Growing. 😃 Also this link may be of use to you https://growithjane.com/bugs-cannabis-plant/

Looks like pests to me

Could possibly be over watered or a pH problem. Is it just one leaf like that or is it all of them, because if it's a few leafs it's fine leafs die throughout the natural canabis growth cycle, if it's all of them you have a bigger problem probably with the roots

Looks like your fan is a bit close or to high, wind burn

Looks like it's had far too much nitrogen...