I think the NRF library, if you use RF24, also has a sort of “multicast” send option, but I’m not sure how that works. It’s supposed to be able to send a messages to all nodes on the network at once. You could look into that.
Anway, short examples of code for sending messages. I’ll leave out the blynk part, but you can imagine that in between the lines, right? 
Sending node:
#include <RF24Network.h>
#include <RF24.h>
#include <SPI.h>
/ RF24 ce, csn
RF24 radio(49, 48);
RF24Network network(radio);
// NRF addressing
const uint16_t controllerAddress = 0;
const uint16_t nodeOneAddress = 1;
const uint16_t nodeTwoAAddress = 2;
struct payload_t
{
unsigned int messageDataOne;
unsigned int messageDataTwo;
unsigned int messageDataThree;
unsigned int messageDataFour;
};
void setup()
{
SPI.begin();
radio.begin();
// Init network on channel 90, with address of controllerAddress variable
network.begin(90, controllerAddress);
}
void loop()
{
// Keep NRF network going
network.update();
// Construct header with destination address
RF24NetworkHeader header(nodeOneAddress);
messageOne = analogRead(A0);
messageTwo = analogRead(A1);
messageThree = analogRead(A2);
messageFour = analogRead(A3);
// Construct message to be send
payload_t payload_0 = { messageOne, messageTwo, messageThree, messageFour };
network.write(header, &payload_0, sizeof(payload_0));
delay(5000);
}
-sorry- pressed Enter too soon, rest of code will be here soon 
This will send the message containing the data every 5 seconds (in this case just a readout of the random fluctuating analog ports).
Receiving Arduino:
#include <RF24Network.h>
#include <RF24.h>
#include <SPI.h>
RF24 radio(9,10);
RF24Network network(radio);
struct payload_t
{
unsigned int messageDataOne;
unsigned int messageDataTwo;
unsigned int messageDataThree;
unsigned int messageDataFour;
};
const uint16_t nodeOneAddress = 1;
void setup()
{
Serial.begin(9600);
SPI.begin();
radio.begin();
network.begin(90, nodeOneAddress);
}
void loop()
{
network.update();
while ( network.available() )
{
RF24NetworkHeader header;
payload_t payload;
network.read(header,&payload,sizeof(payload));
Serial.println(payload.messageDataOne);
Serial.println(payload.messageDataTwo);
Serial.println(payload.messageDataThree);
Serial.println(payload.messageDataFour);
}
}
This should print the values every 5s to the serial screen 
If you want to add a third node, just change the nodeAddressOne variable on the second receiving arduino and send a message to there with the first sketch.
I’ve written it up here a bit more elegant: http://www.instructables.com/id/Lego-Trains-Blynk/
It has the complete source code with Blynk added, you can refer to that too.
