I have a 2013 gen coupe, had the same issue about a year ago. Brake pedal almost to the floor. I took in, was told no issue, press the pedal harder!! At a light, the brakes would slip, and I'd have to pump the pedal to hold the car. Took it in again. I told them to give me new pads on front and back. When I went back later that day, they told me, there was something wrong with the brakes, and they had it for 3 days, gave me a loner, and I got the car back, brakes have been fine since. Was a 2300.00 repair, covered under warranty. (Brake Hydro. Assembly Unit. $2380.00)
I hope this helps.