The extruder is simple enough that I can't see how there's anything wrong with mine, unless both motors actually got suddenly weak. Seems like it might be a mainboard parameter got messed up or something...

How does the calculation for the amount of filament to feed get done? I actually have some steppers that are a little thicker (they'd fit), but I don't know the specs for the FF motors, so they might be a differnet number of steps per rotation, etc.