Brake Warning Light on?

When driving my brake lamp come on

I have a '95 Honda Accord EX 2.2, about 120,000 miles

Since yesterday, I noticed that the red brake warning light comes on when I make a fast turn. It stays on for a little while and then goes away. There seems to be no problem with actual braking performance. I tried several emergency stops from 40mph on a deserted road, and the car braked straight and true.

I recently (within the past year) had experienced the pedal-fade problem, and my mechanic replaced the master-cylinder.

Since it happens only while making sharp or prolonged turns (such as on a highway ramp), I suspect it is a fluid level problem. So I am wondering whether this is basically a leak in the braking system, is that a big problem and whether I should just think about getting a new car?

Thanks

I checked the reservoir earlier this morning and it is at the MIN level. So clearly, the fluid level is low - I can top it off for the time being, but am worried about the root cause.

How big a $$$ is it to get the brake-system properly checked and fixed?

The Brake Lamp on the Dashboard (where usually the 'trunk open' signal is located) is 'ON'. Is there a problem with my brakes? My brakes appear to be working fine. How do I get the light to go off?

Thanks much
Sunny