Btw what is blue wave length. Im new to all this.
Hank
Lights using the blue wave length contain the portion of the light spectrum that plants utilize most for their growth and general life cycle. They do use light from the red spectrum, but a bare minimum of it. You can theoretically grow a plant solely using "red lights", but the plants will be stretched, thin, and emaciated-looking. They struggle just to survive, let alone thrive.
Also, the leaves turning yellow and falling off is natural. It's happened on about 50% of what I've grown in soil (but never in hydro, until the flowering stage). The plant is just sapping energy from the leaves, for one reason or another. They'll yellow, then brown/whiten, and then die. As long as it isn't affecting a good 95% of your fan leaves, you're fine. Just let the plant do what it wants. But keep an eye on it to make sure the plant isn't auto-flowering, and make sure it is confined to the lowest set of foliage.
This is where you gain experience. Observing the plant, and trouble-shooting small problems (and even experiencing the big problems) will teach you more than any grow guide ever could.
~Ethno