XPS L502X Battery

Hi, I own a Dell XPS L502X laptop for almost a year now and in the past two weeks I've noticed that the battery drastically dropped it's runtime from around 5 hours to barely 2 hours... I've checked the health of my battery by pressing and holding the LED button and no light appears (which should mean according to Dell's F.A.Q. that the battery is in good condition, although more than 50% of it's runtime is lost).

I'm using this laptop mainly for listening to music, internet, etc, and also for a few demanding tasks (I work with Audio Workstations), but since I'm only a student not really a lot of heavy use for it yet. I'm really worried because the drop was all of a sudden from one day to another, not gradually as I would expect. I understand that batteries are not supposed to last for as long as the system does, but it hasn't been a year from the purchase (around 10 and a half months). 

Any help and comments would be appretiate. :)