Of the 6 linked to PED use.
4 were for "adderal" use.
Browner
Moffitt (had expired prescription, didn't get special exempt from league)
Irvin
And Sherman (who won his appeal)
Barbe I believe didn't disclose his banned substance, while...
Winston Guy said he took a banned substance from a over-the-counter supplement.
Either way I've done the math and the Carroll had about 150 players churn his rosters over the 4 years.
6/150 is a mere 4% of the players he's coached.
In 2013, only 1 player out of about 70 or 1.4% of the team had a PED incident, and that player passed over 180+ drug tests since May or so and his abuse never did impact the 2013 season unless its the negative result from missing valuable tuning and development time on the field. That's not cheating, other teams probably benefited from Irvin missing that time.