Problem with RGB diodes - low brightness

hi i'm newbie in arduino:) i'm trying develop yourself:)
i bought rgb diodes aliexpress link . i'm playin it, have solder 3 of them , connect arduino uno.
here simple program:

code: [select]

#include <arduino.h>
#include <adafruit_neomatrix.h>
#include <adafruit_neopixel.h>
#include <adafruit_gfx.h>

adafruit_neomatrix matrix = adafruit_neomatrix(3, 1, 6,
 neo_matrix_top     + neo_matrix_right +
 neo_matrix_columns + neo_matrix_progressive,
 neo_grb            + neo_khz800);

 void setup() {
  matrix.begin();
  matrix.setbrightness(50);
 }

 void loop() {
   matrix.drawfasthline(0, 0,  3, matrix.color(255, 255, 255));
   matrix.show();
 }


diodes working if set whitecolor - (255, 255, 255), every next diode changing lite color , blinking. if set lower brightness eg 20, changing lolor , flickering intensifies.

what problem? should diodes light "stable"?

-------------------------------------edited----------------------

i found reason why ther flickering. put code loop() setup() , not fickering. turn on , off leds , make operations in loop, flickering. idea? please help

nobody can help?

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