There is an old saying that goes "Abs are made in the kitchen, not in the gym."
Obviously, Ab Plank, hanging leg raises, ab-wheel rollout, etc. are all great ways to build and strengthen your lower abs. The fact is, however, you can do all of the hanging leg raises in the world, but if you have a layer of fat covering your abs, then you will never be able to see them.
It sounds more like you need to lose the layer of fat over your lower abs, and this is done through having a very clean diet and continuing your workout routing and adding cardio (such as
interval training) to burn extra calories.
In general, to get your body fat down and reveal your 6-pack abs, you should slightly reduce your calorie intake.
The best way to do this is by lowering your carbohydrate intake. This causes your body to switch from primarily burning carbs for energy to burning fat. A general rule of thumb is to lower your calories from carbs to 40% of your total calories per day. The souce below has a calculation you can use to determine how many carbs you should be eating per day.
You should replace some of those calories from carbs with calories from protein. When trying to burn extra fat, you should also get around 40% of your calories from protein sources.
This will leave 20% of your calories for good fats. Some sources of good fats include avacados and olive oil (great on salads!).
These calories should be spread over six small meals per day to keep your metabolism high to burn fat faster.
Keep up your workout routines add some quality cardio, and stay dedicated to a clean diet, and you should see your 6-pack abs in no time!
Source:
http://www.build-muscle-and-burn-fat.co ... k-abs.html