Dorian tore is tricep and can't train anymore. That is why he retired. He probably can do some low intensity training, but nothing like he used to do. He said that his biggest mistake was training too hard while at low levels of body fat, when the body is especially prone to injury.
I don't know what is up with Levrone, but he was never huge. Being well defined and having a good aesthetic build often gives the illusion of size that doesn't really exist, which is what I suspect of Levrone.
I am not saying that it is possible to keep or not keep gains from gear. I am only saying that I don't think it has anything to do with why Dorian is small now and probably has nothing to do with why Levrone is small.
