Mine ate right away but I didn't try anything you listed.
You might want to find out what they were eating before you bought them and try that(besides feeders).
My staple is raw shrimp.
But I agree with whats been posted.
just ride it out. once he settles in and is motivated by his own hunger, he will strike. when i first purchased my florida gar, it went almost 2 weeks without eating. think like a fish. . . (Smile). if you were suddenly placed in a jail cell and not sure of your fate, the last thing on your mind would be food.