If your calipers are leaking you will see the fluid running down the inside of the tire. Without any visual evidence of leakage check all four pads for wear. If they are on the extreme wear side your fluid will be in the lines. If they are super worn then do not top off the fluiduntil you change the pads. If you top off the fluid before putting on pads when you compress the calipers you will send all that fluid back to the MC which then will be over full and will pop the lid off and send brake fluid all over the inside of the engine bay. Brake fluid and paint don't get along. If you do top it off prior to putting pads on besure to drain some out before you compress the calipers.