While running his pass pattern across the back of the end zone, A80 runs across the back of the end zone and steps behind the end line. Defender B1 who is covering A80 follows him out across the back end line. Both then cut back into the end zone in an attempt to catch the pass. Based on 9-6-2, which states that "No player shall intentionally go out of bounds during the down and (a) Return to the field, (b) Intentionally touch the ball, (c) Influence the play, or (d) Otherwise participate", are both A80 and B1 guilty of Illegal Participation, resulting in a double foul and necessitating a replay of the down?