Blynk and FastLED WS2811 Strips

Hey guys,
I'm relatively new to the Arduino world, but I'm thoroughly enjoying myself so far.

I'm trying to control 3 (linked together) WS2811 LED strips (a total of 276 pixels) via my Arduino Uno R3 via the Blynk app for iPhone.
I have no problems running standard light sketches (DemoReel100, etc) or my own custom sketches straight off the Arduino onto all 276 lights, but when I try to use Blynk to control them I seem to only be able to control 70 pixels, after which (when I up the NUM_LEDS value any higher) they don't respond anymore.
Could this be a memory problem? When I verify my sketch it says I'm using 32% of program storage space, and 62% of dynamic memory.

Any ideas/suggestions would be greatly appreciated.

Here is my code:

#include<FastLED.h>
#include <BlynkSimpleSerial.h>
#include <SoftwareSerial.h>
SoftwareSerial SwSerial (2, 3); // RX, TX

#define NUM_LEDS 70
#define DATA_PIN 8
#define LED_TYPE WS2811
#define COLOR_ORDER BRG

int varHue = 0;
int varSaturation = 0;
int varBrightness = 0;

CRGB leds[NUM_LEDS];

char auth[] = "b8380ea6419e4406904989aff698029a";

void setup()
{
delay(1000); //LED safety delay
FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS); //for correct LED strips
Blynk.begin(auth);
}

BLYNK_WRITE(V0)
{
varHue = param.asInt();
}
BLYNK_WRITE(V1)
{
varSaturation = param.asInt();
}
BLYNK_WRITE(V2)
{
varBrightness = param.asInt();
}

void loop()
{
Blynk.run();
fill_solid(leds, NUM_LEDS, CHSV(varHue, varSaturation, varBrightness));
FastLED.show();
}

Could this be a memory problem?

Yes, it could. Compile the sketch with NUM_LEDS set to 10. Note how much memory is used. Compile the sketch with NUM_LEDS set to 20. Note how much memory is used. The difference is how much memory is needed for 10 LEDs. Show the results. You should be able to determine, then, how many LEDs in all you can support.

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At 70 LEDs, interrupts are going to be blocked for 2ms. I suspect that causes data coming in from the iPhone to be lost and may be causing the blynk library to hang up.

As far as memory usage, each led takes up 3 bytes of ram - so 70 LEDs would use 210 bytes of ram, 276 LEDs would use 828 bytes of ram, etc... I don't know how much memory blynk will want.