Controlling 4 BLDC with arduino uno.

Hey everyone.
I am using arduino uno to control speed of 4 bruslessdc motors. i am using this libraray to generate 50Hz (which is desired for motors) on pwm pins. http://forum.arduino.cc/index.php?topic=117425.0
but i am having a problem. i get 50Hz frequency on all 4 pins, but the code doesn’t seem to enter in loop to change the duty cycle between 1ms to 2ms which is required by my project. if i write pwmWrite command outside loop by giving only one brightness value (duty cycle) then it works fine. if someone can help me please, i will be very thankful.
here is my code.

#include <PWM.h>
int32_t frequency = 50; //frequency (in Hz)

void setup()
{
//initialize all timers except for 0, to save time keeping functions
InitTimers();

//sets the frequency for the specified pin
SetPinFrequency(3, frequency);
SetPinFrequency(5, frequency);
SetPinFrequency(9, frequency);
SetPinFrequency(10, frequency);
}

void loop()
{
for (int brightness=13; brightness<=26; brightness++)
{
pwmWrite(3, brightness);
pwmWrite(5, brightness);
pwmWrite(9, brightness);
pwmWrite(10, brightness);
delay(30);
}
for (int brightness=26; brightness>=13; brightness–)
{
pwmWrite(3, brightness);
pwmWrite(5, brightness);
pwmWrite(9, brightness);
pwmWrite(10, brightness);
delay(30);
}
}

Which motors? We cannot guess this.

A28L Brushless dc motors http://www.hobbyking.com/hobbyking/store/__8474__a28l_brushless_outrunner_920kv.html

OK, now we've established they are RC brushless motors, which ESCs are you using? Do they not like the Servo library?

ESC used is 18A plush series.