problem using one function to blink different leds
You want to let the LEDs blink concurrently.
Your static variables oldTime, and ledState are shared between the three LEDs.
So there is ony ONE ledState in your program but you need that state for each one.
Same applies for oldTime.

Resolve the this issue and your LEDs will blink as expected.

btw. you don't need the ledState as you can read its current state.