What could those spots be? They came out on the ol...

thrips damage

Hard to tell.... My first suggestion would be thrips. But I'm not 100% sure. Thrips suck the chlorophyll out of the leaves. You always can spot black spots on the leaves, that is the shit from them. But it is not white powdery mildew for sure

THRIPS and NOT powdery mildew! Insect damage.

Looks insect of some type to me. I had a issue like this recently. I used neem oil and a few drops of soap in water mix. When plants hit their dark time I just took the plants and sprayed them down everywhere. Heavily. Then I let them dry during dark cycle. My problem was solved at low cost.

And btw, Dr. Zymes is also a fungicide so if you ever DO get a fungus, it will take care of that as well....

That is DEFINITELY NOT powdery mildew... not on your life! Those are insects (and thrips to be precise) and they need to be gotten rid of quick time. Grab yourself some Dr. Zymes Eliminator or, if you can't get that where you live, some Spinosad.... both are organic, both can be used without damaging anything (except the insects) right up to harvest ... they will kill the adult/larvae/eggs of thrips, spidermites, aphids and whiteflies and it's always good to have one of them on hand. Just spray as directed just before lights out.... Cheers...

White powdery mildew. Usually caused by your humidity being too high. In depth diagnosis and cures explained here (and elsewhere on the Web if your prefer): https://www.growweedeasy.com/cannabis-plant-problems/white-powdery-mildew