Bottom leaves dying can be normal. It's an issue when you start seeing multiple leaves showing signs of deficiencies or toxicities. I'm doing an all organic grow right now but, when I did feed bottled nutrients, I was happy with the Sensi line from Advanced Nutrients dosed once a week at half the recommended dosage (I grow in soil). Most new growers feed way too much, and too often, and that's where a lot of their issues come from.