Brake lamp lighten on dash?

[Valphi]

Good day all, I have a Montana SV6 2006 3,5L. I did my brakes last year and it's been a couple of month that the brake lamp light once in a while in the dash. Now, it's been 2 days that the lamp stays lighten. I've checked my brakes and everything seems ok. What sould I chek next? Thank you for your advice. )

 

[Zimgxp]

How is the Fluid Level?

 

[Valphi]

How is the Fluid Level?

I've checked the level before posting. I add maybe 1/2 of an oz. Still showing red warning that indicates to get the brakes check. :/

 

[melsg5]

did you pull each wheel off and checked the calipers/cylinders for leaks?
did you trace each line from the master to the abs unit to the wheels looking for a leak?