@cobalt I agree with what's said above. My immediate guess is serrano on the left, jalapeño on the right.
I know that with inferno peppers (my favorite), the longer you leave it on the plant the hotter it gets. I have no idea whether that´s true for other peppers.
My experience with jalapeños is you never know what will happen when you bite into it. One will be 500 SHU, the next one 8000 SHU.
Have you ever wondered how every jar of (pick a brand) of pickled jalapeño slices has the same amount of heat? How do they manage that?
Turns out there's a cultivar of jalapeño that has zero heat and it's the most widely farmed for commercial use. You guessed it. They use zero heat peppers and add capsaicin to set the heat at any level they like. Sometimes these find their way into the produce department.