It's hard to watch your friends get sick while you stay well.
Some people even feel guilty in that situation.
There are a number of things you should keep in mind. Even if you and your friends all got tested on the same day, there may still be years of difference in how long you've each been infected. Second, there are very few diseases that behave the same way in everyone. And of course, it's becoming very clear that the kind of medical treatment you get makes a big difference, too. You may still be angry and sad when you see your friends get sick, but it's nothing to be surprised about.