Mr. Brooks's NetLogo Design/Style Laws

Thou shalt not need 2 forever buttons going at the same time for any visual effect.

Thou mayest have many forever buttons, but never have more than one running at a time.

Therefore, you'll have to design your programs to need only one forever button going to show whatever you want to show.

Why is that, you asketh?
Because each button is trying to have its own commands running as quickly as possible, and they will compete, with unpredictable results.

...and it goeth without saying that...
Turn off your forever buttons before making any modifications, particularly in code.
Imagine if your brain was being modified while you were speaking.
Two forever buttons pressed
Each button shall call only a single procedure in the code tab.  No other code in buttons.
It's much more difficult to debug code that's inside buttons than inside the code tab.

Furthermore, every button must be in observer mode.
This is because it's easy to get mixed up between modes.
Too much code in buttons
Each command deserves its own line in the code tab.

It will be a pain in the posterior to debug lines with multiple commands.  Get used to doing it this way to retain your sanity later.

BTW, note the placement of opening and closing brackets vertically above each other when enclosing more than one command.  This makes it very easy to understand what closing bracket belongs with what opening bracket -- bad placement of brackets is a universal source of debugging problems.
One line per command