It is very laudable for you to wish to help others in the future. Medicine is an imprecise art and science and there are many disease conditions that we do not understand. As physicians, we need to be humble to the fact that we do not know everything and that we need to constantly learn to improve. The best way to improve quality is education. I personally would not be insulted if you were to send me a letter to inform me (nicely) of your final diagnosis. I would incorporate that into my information data base and be more ready for the next similar situation. If you do not inform these 2 physicians, they may never be aware of their missed diagnosis.
Hope this helps and thank you.