I had the same problem you did. If u really want to gain mass, increase your calories. Since u seem pretty lean, so I bet u have a high metabolism. It would be a good idea to multiply your weight by 20 and eat atleast that many calories (3330) everyday for a week. Only do legs once a week. I know this may sound strange, but stay away from leg presses. Do squats instead and you will see a big difference. Tony