Make adjustable mosfet constant current source
You could achieve a superior result making an adjustable current source following this circuit design. Replace the R1 and R2 resistors in the following with a 100K pot to allow for adjustability. 



The U3 component is a shunt regulator that produces a fixed drop of 1.25V when biased at current as supplied through R0. This shunt reference part can be substituted with other similar parts that would have a 1.2 or 1.25V rating.

With a 100K pot set at 72K/28K as shown the current in the output LEDs will be ~350mA. 

Note that I have changed the current sensing resistor from your original 2 ohms to 1 ohm.

The opamp shown is a 1.2MHz bandwidth device with rail-to-rail inputs and outputs. It may be replaced with another part number with similar characteristics. 

The shunt regulator can be shared with multiple LED current sinks. If you go over three or four shared circuits it would be necessary to decrease the value of R0 so that the bias current of the shunt regulator is increased. It is a good design practice to have the current through the shunt regulator to be 5->10 times larger than the current through the pot (i.e. R1 and R2 divider).