Youtube is the worst place to learn about growing cannabis. Ever notice how many videos show plants with crispy fried leaves at harvest. Any hack can post videos. And most everything else is an infomercial pushing some product. Many of those guys are sponsored to push products.
Cannabis is a plant and nothing special. It doesn't require all this cannabis bro-science. You'd be better off learning gardening basics and basic plant science than watching some dude on youtube using fancy overpriced products to grow overfed nasty looking plants.
I took a peak at one of those youtube hacks that a bunch of people were talking about as if he was some kind of growing guru. He's nothing more than a hack that can't grow worth a crap. Here's a screenshot from one of his videos. And some people think he's a good grower.