[86.5 7MGE]

Ok so yesterday I was driving back home and as I'm going about 65mph+ I go to slow down and my brakes feel spongy real soft. That morning I didn't have any problems with my brakes. As I'm driving through town this morning I have nice firm brakes about 30mins later when I enter the freeway and I go up to 75mph+ I had to stop quickly when a car cut me off and to my surprise yet again no brakes, as the pedal traveled from about an inch from the floor I could feel the front ones engage and not the rear with loss of pressure. I got out when I stopped and check my fluid level and it's within the specified range between min and max. Can someone help me out on this? Thanks for all your helpful inputs.