"Brake Applied - Power Reduced" - I mean aside from the obvious...
The issue may be around the brake caliper and if you have drum brakes to the back, Wheel cylinder.
Do you hear grinding noises or feel a pull in the steering (left or right or even a shudder) when you apply the brakes ?
Else this could mean anything from a bad hub/bearing/Tone wheel (ABS or Speed sensor at that hub) that can make the system think you're crippled and or something in the brakes is wrong but has not set the BRAKE light yet because it's not directly with the Braking as in Fluid losses - but in how the system perceives braking effectiveness which is the issues of Hub/Sensor issues.
So will need some further info to help find a solution