Your plant looks great. Stop being paranoid. Most leaves look like that. Once the plant gets bigger, they will drop off, and as the plant continues to grow, it will drop more and more bottom leaves if there is no adequate lighting. You also should wait until the top soil is dry, and the bottom soil is slightly moist before each watering. This allows for roots to get oxygen much more efficiently. Or, if you do not want to worry much about over watering, place an air stone into your water bucket a day before watering. This will mix air into your water, and provide more air to your roots when you feed the plants. Pump and airstone costs less than 10$ in an aquarium store. Get on it cowboy.