Flow Meter in GUI doesn't work

You are pointing in the right direction but all this code does is to lose whatever number was in count1 by setting the value back to zero

 noInterrupts(); //Disable Interrupts
  count1 = 0; //count variable for flow meters
 
  interrupts(); //Enable Interrupts

You need something like

 noInterrupts(); //Disable Interrupts
  latestCount1 = count1;
  count1 = 0; //count variable for flow meters
 
  interrupts(); //Enable Interrupts

...R