It is essentially impossible to prove PED use in elite sports because athletes take care not to get caught and there is no interest in catching them.
I don't know much about gymnastics but if performance in that sport is dominated by strength or endurance, that is a stronger or better conditioned athlete will normally win, then it is likely that the top athletes in the world use PEDs. Otherwise it would be inconsistent with evidence of PED use in every other strength or endurance sport.
I don't know why you think having competed against an athlete would give you some special insight into their PED use especially if you aren't competitive enough to beat them; it would clearly be precarious to have other people find out.
I don't know much about gymnastics but if performance in that sport is dominated by strength or endurance, that is a stronger or better conditioned athlete will normally win, then it is likely that the top athletes in the world use PEDs. Otherwise it would be inconsistent with evidence of PED use in every other strength or endurance sport.
I don't know why you think having competed against an athlete would give you some special insight into their PED use especially if you aren't competitive enough to beat them; it would clearly be precarious to have other people find out.