If you replace the function MeteorRain with this does it make a difference?
It basically swaps the outer loops:
void meteorRain( CRGB ColorBackground, CRGB ColorMeteor, byte meteorSize, byte meteorTrailDecay, boolean meteorRandomDecay, int SpeedDelay )
{
// set background color
for( uint8_t i=0; i<NUM_STRIPS; i++ )
fill_solid( grLeds[i], NUM_LEDS_PER_STRIP, ColorBackground );
for( uint8_t strip=0; strip<NUM_STRIPS; strip++ )
{
for(uint8_t i=0; i<NUM_LEDS_PER_STRIP*2; i++ )
{
// fade color to background color for all LEDs
for(uint8_t led=0; led<NUM_LEDS_PER_STRIP; led++ )
{
if( (!meteorRandomDecay) || (random(10) > 5) )
{
grLeds[strip][led] = fadeTowardColor( grLeds[strip][led], ColorBackground, meteorTrailDecay );
}//if
}//for
// draw meteor
for( uint8_t j=0; j<meteorSize; j++ )
{
if( ( (i-j) < NUM_LEDS_PER_STRIP) && ((i-j) >= 0) )
{
grLeds[strip][i-j] = ColorMeteor;
}//if
}//for
FastLED.show();
delay( SpeedDelay );
}//for
}//for
}//meteorRain