Could be roids. When I used to powerlift that stuff was all too common. When I was kid lifting with the grownups they sold GHB next to the protein bars.
It's definitely the corona virus lockdown mandates. To me, with the mention of papering over the windows _so no one could see the no masks on inside_, it 100% indicates that they wanted to make sure he wasn't going to call the police and get the gym shut down. The people wanted a gym community and so they built one while heavily vetting who was allowed to know about or enter the space, specifically so they could avoid the eyes of the government during the lockdowns.
Yes my thought was juicing. Beyond the obvious bodybuilders in gyms the world over, when fitness is needed past a certain level of seriousness it’s much more common than expected.