I guarantee you practically none of them ever stopped. Not for long anyway. The huge drop off in performance across the board by many top fighters was more of a result of having to adjust to the new system and some like Vitor not being able to find anything that would maintain his past results. He was genetically played out.
Within a relatively short time USADA was gamed as fuck.
Now you have athletes micro dosing and they have to be complete morons or make enormous mistakes with their cycles to get caught. You don't even need bioidentical hgh or test to avoid getting caught. Just don't be a careless idiot like Jones.
All those tests for EPO on TJ's past samples that USADA cleared him on, that everybody brings up as some sort of vindication, don't mean dick when the window for catching it in a test can be measured in hours, at the amounts they are dosing, at the very most.