I max out with 10 mg melatonin. That it is a potent antioxidant is a welcome side effect.
L-arginine is not ordinarily considered a substance that has much to do with somnolence. But I and others, initially taking it for something else have noted the effect.
Do you have a preferred brand of CBD? I’ve tried several brands and types (edibles, tinctures) and thus far there are none I’ve been especially pleased with.