I see a couple white spots. Do they rub off? Check under the leaf as well. More then likely it’s water droplets from watering and the light intensifies the droplets burning/staining the leaf.
Water on leaves & light are a no-no.
If the spot doesn’t rub off then it’s not powered mold. Powdery mold spreads very fast.
Overall I’d say you’re doing a fine job and the plant is definitely up to par + for only 21 days
Good Luck 
Thankyou and no they don’t rub off I’ll try to keep the humidifier down i appreciate that.
The clone isn’t from an auto flower.
Any one ever dealt with root aphids? How do you deal with them?
I hate to break it to you, but autos are not easier. A bit more convenient that you don’t have to have a light sealed room for them but any hiccups can’t be made up due to them flowering as soon as they are sexually mature. With photos, you can keep them in veg until ready to flip to flower. Good luck, any plant is fun to grow!
They are definitely set on go from time the seed pops. Just let them do what they are going to do and take care of them and let them go. They will surprise you in a short time lol
Pyrethrin applied as a soil drench every 3 days for three applications will kill them.