I was driving around town today when all the sudden when a "Brake fluid low" message displayed on my dash. I still had braking power, but I noticed that the pedal when depressed would slowly drift to the floor. I got home safely, but by then I've noticed there's no resistance or braking power until it gets all the way to the floor, then I will get braking power. The fluid reservoir was about 2 inches below the "low" line. I've looked, but haven't readily found an obvious place brake fluid is leaking in my lines. To be honest, I've never really checked the brake fluid level in a couple years (yes I deserve a flogging for that) so I don't know if the low fluid level is new or a chronic issue. Do I most likely have a leak, or is the low fluid level misleading and its actually a failed master cylinder? Could someone please weigh in on the most likely issue? Thanks!!