Is there any other way to check?
A few maybe. Most meters are more accurate measuring voltage and current then ohms. So if you wired a series 100 ohm resistor (any size to lower the series current) with your low ohm resistor(s) and wire it to a stable regulated DC voltage of 5vdc. Then measure the voltage drop across the low ohm resistor(s), and then measure the current in series with the voltage source, you can then calculate what the low ohm resistor is, R = Vr/I.
Resistors will even change their value a little depending on what temperature they are running at, and at 300ma you are heating them up a bit, no?
Digital multimeters quality and accuracy varies with cost of the meter.