When I did more weightlifting me and some other guys got stuck at around 75 kg and couldn't put on more weight no matter how hard we trained. A few months later two guys jumped to 90 kg in a very short time. I asked what's going on and they told me they got some stuff from Poland. I assume either steroids or HGH.
PEDs are way too effective for somebody to be able to compete against people who take them. It's simply not possible.
In the 100m a lot of top 10 guys got caught or evaded tests in the last years. There is no way that Bolt is beating them without taking something.