Until the clubs themselves are punished for positive tests of their players, the club has NO incentive to monitor closely it's players, while simultaneously incentives push players to use PEDs (on the one hand there is potentially generational money, on the other hand the morality of a player wanting to compete clean).
At the MLB level, a positive test should mean a team loses a spot on the 25 man roster for the length of that player's suspension. For MILB, the last club the player played for should have their roster trimmed by the number of players who tested positive. Alternatively, a significant monetary penalty could be imposed on the parent club for each positive test - I'm talking a painful amount, designed to create an incentive for the clubs to pay attention, rather then ignore a known problem.
Right now, baseball is playing (and knowingly playing) whack-a-mole, with penalties ONLY being felt by the player; once the penalties are felt by the clubs, the field might get a bit more level.