Johnny Go had fallen at the first fence and ran loose before coming down on the run-in. He was being treated while the race was being run and suffered a fatal injury.
'Stop-race' procedures were put into place by the racecourse executive while Johnny Go was being attended to behind screens near the finishing line, with the race subsequently declared void.
But Quinlan, rider of first-past-the-post Red Giant, Fox aboard Miss Joeking - the only other finisher - and Mulqueen, who was unseated from Here Comes Love after the final fence, appeared to ignore the 'stop-race' flag waved to raise attention to the stricken horse and were hit with hefty bans.
Paul Struthers, chief executive of the Professional Jockeys Association, tweeted: "An appeal on behalf of Stephen Mulqueen, Sean Quinlan and Derek Fox against decision of the stewards at Perth has been submitted."
The British Horsracing Authority confirmed the appeal would be heard on September 21.