Once the jacks are mounted to the chassis, they are grounded, and require no ground wires.
Mount each jack with a tooth lock washer behind the front panel. A flat washer belongs on top of the front panel, under the nut.
Tighten it good.
Now all four jacks ARE grounded...
Fiber washers are used so each jack does not touch the chassis, OR plastic jacks, like CLIFF jacks.
A Ground wire connects to the four jacks, then goes to the central preamp ground point,
The same ("star") point that all preamp circuit grounds connect to.
Using the "star" method, connecting the preamp circuit grounds AND the jack ground to one point,
you probably do get less noise, less HUM.
BUT this is not needed in a normal Fender design amplifier. The traditional Fender design is pretty low gain.
The HUM does not show up, and is not amplified to the point of distraction.
In amps with very high gain, the HUM will be amplified much more, the star method can reduce the hum,
at least to a tolerable point.
And since you are not building a really high gain amplifier, grounding the jacks to the chassis is probably just fine.