Q. Can the lights flash rate be adjusted independantly?
A. Hi Peter, thank you for your question.
If you look at the circuit diagram on the data sheet https://www.rapidonline.com/pdf/70-4138.pdf the variable resistors are used to influenec the charge /discharge rate of the capacitors C1 & C2 – which in turn load the bases of the transistors- which act as switches for the LEDs.
They therefore affect the time interval between the leds flashing – so in a manner of speaking they do control each one – but they are dependant on each other – you cannot adjust one without affecting the other.