Welcome to the forum 
I would say that the problem is due to frameRate that you have in the processing loop and the ODR (output sample rate) that you have from your arduino.
From the arduino side you are sending the signals at which frequency?
You should also take into account the baud rate when sending data to ensure that all signals are being sent within the buffer capacity to output your data.
The processing frame rate of the loop is by default 60fps but you can change this using the frameRate method to define your own.
The maximum frameRate will depend on the sketch you are running as well as the machine. So, try to avoid at least duplicated code (like join all text with the same text size and you don’t need to redefine the stroke at all times, if the color of the text is always the same). One test that you can do is print the frame rate and modify your code to see how is it affected
So in your case, and depending on your frequency from the arduino. You can modify the setup like this:
void setup(){
size(1024, 600); //Tamanho da tela LED IVO M101NWT2 R1
port= new Serial(this,"COM7",9600);
frameRate(?????) //PLACE HERE THE DESIRED FRAME RATE
background(0);
}
Also, the following link might be useful to you as well
Best regards