Wow. Just from looking at it, it seems the only thing it could be is brake fluid. But this must be a slow leak if you still have fluid in your brake fluid reservoir. The pictures seems to show this happening over a time period and not all at once, given the discoloration. Is that true?
Is your bike still under warranty? Looks like you have the stock brake lines still on it. My advice would be try and get suzuki to warranty it, unless you were monkeying around with the brake lines. I believe these bikes had a recall from the 2015-early 2016 models for something to do with the brakes. Maybe someone else can chime in about that.
The Dude Abides and Rides:
2017 Suzuki GSX-R 1000-Blue