I've noticed over the past couple of days that the pedal seems to sink down more than usual on the first hit of the brakes. If I'm in traffic or going from stoplight to stoplight it's fine. But if I'm cruising for a little bit and then go to hit the brakes, the pedal sinks down noticeably more than usual on the first push but if I let off quick and hit the brakes again it's fine. I'm thinking maybe there's an air pocket in the lines somewhere? I haven't touched the brakes at all other than pulling the caliper off the bracket when I put my iso's back in. No lines have been touched etc. After I put them in is when I noticed the issue. The front calipers have been on and off the brackets many times for suspension/spring changes and adjustments with no issues at all, this is the first time this has happened. Any thoughts?