here here can replace a fet on a JL 250.1

[DBDRAGGUY 10+ year member]

IIRC There are no markings on the fets JL used in those amps, so there is no way to tell what you would replace them with...
sending it into a JL authorized repair center is probably your only option... and BTW, rarely will only one or two fets blow..

This is true, best bet is sending it back to JL or an authorized repair center. And rarely does a fet just go out on its own.