My brake fluid level is below the "Low" mark which is causing my brake light to come on...(I'm pretty sure thatz the reason why). Anyways my question is, is it ok to just take off the lid and add some more brake fluid? Or do you think I should have my brakes serviced? They were serviced about an year ago and the guy said the front pads have alot of life left on it but the back ones were replaced. What could be the cause of this leak and is it ok to just add more brake fluid?

P.S. Can u find Dot 3 or Dot 4 brake fluid at like Pep boys? Does brand really matter? Not quite sure what the brake fluid brand is