Error: a function-definition is not allowed here before '{' token แก้ยังไงครั้บ

#include <Wire.h>

#include <SoftwareSerial.h>

#define RE 8
#define DE 7
// Uncomment whatever type you're using!
//#define DHTTYPE DHT11 // DHT 11
#define DHTTYPE DHT22 // DHT 22 (AM2302), AM2321
//#define DHTTYPE DHT21 // DHT 21 (AM2301)
const byte nitro[] = {0x01,0x03, 0x00, 0x1e, 0x00, 0x01, 0xe4, 0x0c};
const byte phos[] = {0x01,0x03, 0x00, 0x1f, 0x00, 0x01, 0xb5, 0xcc};
const byte pota[] = {0x01,0x03, 0x00, 0x20, 0x00, 0x01, 0x85, 0xc0};
SoftwareSerial espSerial(5, 6);
int nitrogen();
int phosphorous();
int potassium();
String str;
byte values[11];
SoftwareSerial mod(2,3);
const int PUMP1 = A0;
const int PUMP2 = A1;
const int SOLENOID1 = A2;
const int SOLENOID2 = A3;
byte val1,val2,val3;

void setup(){
Serial.begin(115200);
espSerial.begin(115200);

pinMode(RE, OUTPUT);
pinMode(DE, OUTPUT);
pinMode(PUMP1, OUTPUT);
pinMode(PUMP2, OUTPUT);
pinMode(SOLENOID1, OUTPUT);
pinMode(SOLENOID2, OUTPUT);


}
void loop()
{



str =String(values[11]);
espSerial.println(str);


val1 = nitrogen();
delay(250);
val2 = phosphorous();
delay(250);
val3 = potassium();
delay(250);


if(val1,val2,val3<=20)
 {
  digitalWrite(SOLENOID1, LOW); // turn on solenoid2 10 seconds
  digitalWrite(PUMP2, LOW); // turn on pump2 7 seconds
 }
if(val1,val2,val3>20)
 {
  digitalWrite(SOLENOID2, HIGH); // turn on solenoid2 10 seconds
  digitalWrite(PUMP2, HIGH);  // turn off pump2 7 seconds
 }

                 

byte nitrogen(){
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
delay(10);
if(mod.write(nitro,sizeof(nitro))==8){
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);
for(byte i=0;i<7;i++){
//Serial.print(mod.read(),HEX);
values[i] = mod.read();
Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}
 
byte phosphorous()
{
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
if(mod.write(phos,sizeof(phos))==8)
{
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);

for(byte i=0;i<7;i++)
{
//Serial.print(mod.read(),HEX);
values[i] = mod.read();
Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}
 

byte potassium(){
digitalWrite(DE,HIGH);
digitalWrite(RE,HIGH);
if(mod.write(pota,sizeof(pota))==8){
digitalWrite(DE,LOW);
digitalWrite(RE,LOW);
for(byte i=0;i<7;i++){
values[i] = mod.read();
Serial.print(values[i],HEX);
}
Serial.println();
}
return values[4];
}                     
}

error

C:\Users\Admin\Documents\Arduino\ssr3\ssr3.ino: In function 'void loop()':
ssr3:71:16: error: a function-definition is not allowed here before '{' token
 byte nitrogen(){
                ^
ssr3:89:1: error: a function-definition is not allowed here before '{' token
 {
 ^
ssr3:109:17: error: a function-definition is not allowed here before '{' token
 byte potassium(){
                 ^
exit status 1
a function-definition is not allowed here before '{' token

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