Your leds should flash at a normal rate with the flasher relay. I have one on my bike and it works without resistors.
Does the rear taillight have at least one ground wire? If it doesn't then it's faulty and you need to contact the company that you got it from.
First thing I would do is make sure you have the correct flasher relay. Make sure it's the one made for FOUR components.
Second get rid of the resistors.
Third check that the front signals are wired correctly.
Last, make sure all the ground wires(from the bike brake light and signal wiring) are connected to the one ground from the aftermarket taillight. Hook up the signal wires to the corresponding left right signal.
If this doesn't work then your issue is beyond my expertise.
The above is how I did my aftermarket light set up and I've had zero issues.