You can, but if it's not your personal opinion and the person using this reasoning can accept one result but not the other results that follow, there are problems with that person's consistency, or with the argument.
If you base on past indiscretions, and the possibility of an undetectable chemical x, as well as the idea that Occam's Razor says that extremely impressive performance is simpler to explain through chemical x, then you should apply that reasoning to all cases that you encounter that have these characteristics, because your reasoning would say that it is possible they are on drugs.
Specifically, you have to judge Ledecky guilty until proven innocent, since the USA has a proven steroid use history, Ledecky cut 20 seconds off her time, her teammate was convicted of doping, Ledecky has theoretical access to undetectable chemicals etc.
Then you'd have to apply your consistent reasoning to Bolt (Jamaican steroids), Phelps etc. If your argument cannot be applied like that without the person using it accepting the results, there's a problem with consistency. The argument could be right, but the person using the argument would not be consistent. Alternatively, the argument may be rejected if it leads to absurd consequences.