I have a 1995 EX Accord which may need a brake master cylinder. I'm
not sure about this because just two weeks ago I had my front rotors
and brakes replaced. Could it be that the mechanic did not bleed the
brakes correctly, and that there is air in the system?

When I press on the brake it goes to its expected place and then
slowly goes down further, until it reaches the floor. This only
happens sometimes, usually at long stop lignts.

Can someone help me out with this.