All those lowest bottom leaves are called mud lugs. They always turn brown and die first. They are usually very thin, tattered, dirty, low in nicotine, and low in flavor. I usually recommend first time growers experiment with curing them to gain a little experience in the curing process before the real leaf is ready so you will be a little more confident in curing and can make mistakes with leaf that’s not much good. After that first season, most guys just toss them because they’re hardly worth the effort. It is pretty cool to roll up a stogie in the patch from a mud lug that has fully cured on the plant. It feels pretty special to sit in your patch smoking your leaf you just plucked off your own tobacco plant.