i just went throu exact same thing..exceptionally yellow feet on chicks..when i hatch mine they come right out of shell with pinkish white feet sometimes a few freckles...these were yellow so gave them all away...the kids i gave them to told me last week the foot soles had turned quite light..not sure what was going on there..
The yellow to pinkish feet don't necessarily make them jersey giants. The color of the feet can change to the correct color. It is also not standard of perfection but not a breed determinant.
If they are Jersey Giants, they will be much bigger than australorps at a year old, by up to several pounds. They also wont have the Australorp shape.
At least one of them has the curvy shape so I lean toward BAs.
One of the might be a cockerel though.
Ron