Not getting expected voltage at LED
Arduino outputs are typically limited to 20mA with a voltage drop of 0.3 to 0.8V  depending on the microcontroller used.

For 350mA leds, you need at minimum a mosfet or transistor, and preferably a constant current driver.

Resistor voltage dividers will be very very poor in this type of situation. You'd be better off using just a single resistor.