Powering LEDs, dim LED in parallel
The solution for this is to use a higher supply voltage.

If there is a large voltage drop across the resistor, then small variations in the forward voltage of the LED will cause relatively small variation in the voltage across the resistor, and therefore small variations in LED current.

With a supply voltage close to the LED forward voltage there must be a very small voltage drop across the resistor, so that small changes in LED forward voltage cause large changes in resistor voltage, and large changes in current. So, LEDs that have a bit higher forward voltage get significantly less current and appear dim.