Can someone help my browning new plant?

I'm a new grower and my first plant seems to be having some problems. I put it under 2 100watt equivalent cfl lights and it seems to be growing new leaves but also turning brown and two leaves crumbled and fell off. I water it with tap water like twice a day

You are overwatering your plant. In other words, you are drowning it. Less is more. Just leave it alone for like four days. Then, after four days, stick a finger in the soil to see if it's in need of watering. If it's still moist in the top two inches, then leave it another day. If it's dry, then give it a little water. Never water more than once in a 24 hour period. You might have other problems like root rot to deal with if you've really watered it too much.

Thanks you! Should I keep it under the lights 24 hours a day?

24, 20, 18, whatever you want, just remember what you do to expand your knowledge for your next grow