Fitting them independently is trivial; you can see the result in the attached plot.
That’s great already! Can you maybe share the script that produces this plot, so that we can better understand the problem, see how it is different from the tutorial you linked, and then give targeted advice.
Thanks for your quick answer. I tried to scrape down my code to make a minimal working environment.
I can also provide ROOT files to make it run using them if needed. But the overall structure is here.