All three brake lights not working properly

Brake lights slow to light up when pedal is pressed. When car is in park, stepping on pedal they work. When car is in reverse, takes more pressure on pedal to get them to light up. Overall it seems like more than usual pressure on pedal is needed to get them to light up. Checked brake fluid, full. All bulbs good, they all light up, all were replaced about a year and a half ago. Left and right signals work fine. Back up light (white) works. Brakes themselves work fine. Fuse? Switch at the pedal? Thank you for your time and help!